[This blog post was written in April 2011. Since then twitter and identica have drastically changed the look and functionalities of their services. The following text is more or less outdated.]
Identica and twitter are two micro-blogging platforms people use to dent / tweet 140 characters messages, subscribe to other people whose posts they like, to share them (ReDent / ReTweet) and reply to. Both platforms have a rather specific design. And with these differences in design a very simple question arises: Why is it that the platform specifically designed for discussions (identica) has far fewer users than the platform that is suited only for statements (twitter)? In what follows I don’t give a concluding answer but some suggestions stemming from my time with identica..
There are enough papers on the structural differences between both services and many on an appropriate technical level. I will not go through them. In fact, I don’t want to talk about identica and twitter from a geek’s technical perspective at all, but from the perspective of a user who has no knowledge of programming or of the history of a specific software.  In what follows I give some observations from a layman’s perspective on the usability of both platforms.
Identica and twitter are similiar but different in critical areas that distinguish them in usage and audiences. As the design differences have often been told, I touch them briefly, only to add something here and there.
1. Actualization : Identica actualizes the statuses in real time while twitter only informs about new tweets. ]
2. Context : In twitter one finds the tweet that provoked an answer by clicking on the link “in reply of”. It opens the tweet, clicking on its “in reply of” opens another. These replies are rather “linear”: even if a tweet has two or more replies one will see only one at a time. Finding other replies to the tweet is rather laborious. In identica all replies to a dent are listed in one Conversation-page that depicts the dents and their relative position to each other in a hierarchy. One main difference to twitter is that you see every reply to a dent regardless whether you’ve subscribed to their author or not. Due to this a coversation may create a rather complex page; the decision to indent and to place the reply directly under the dent it replies to creates rather lengthy and sometimes unclear pictures.
3. Nakedness : This is my term for identica’s particularity to show everything a person you’ve subscribed to does (with the exception of Direct Messages).  Unlike twitter that masks the @-messages of a person you’ve subscribed to to a third person you haven’t subscribed to, identica shows all these @-messages in your Personal Timeline. RTs / RDs are handled differently as well: twitter doesn’t show the RT of a third person via a second person, if you’ve subscribed to both. Identica repeats every RD even if you’ve subscribed to all persons involved. Accordingly, it is sometimes possible that exactly the same message (not only a graphical variant due to a different client) comes up several times in the Personal Timeline. Furthermore, @-messages to you of people you haven’t subscribed to show up in your Personal Timeline whereas on twitter they are put aside in a specific @YourAvatarName-line.
These three features combined make identica far more than twitter to be something like a chat: real-time actualization with the use of Context, i.e., so-called “conversations” in which everybody can “dent into” and reply to messages of people he otherwise wouldn’t have even known to be a part of the debate. 
4. WTF : In twitter you get suggestions whom (not “who,” you morons) to follow, taken from the subscriptions and subscribers of the people you’ve already subscribed to. On identica there is a Public Timeline and a Popular Timeline instead, in which one may find interesting people. Notes on the Popular Timelines are pushed upwards by overall favorizing, not by redenting, whereas the notes on the Public Timeline are published simply in order of their being posted
5. Groups : This feature of identica should be well-known by now. Whereas twitter uses Lists besides the one Personal Timeline, identica has Groups. With Lists you collect interesting people in a read-and-reply-mode list, regardless whether you’ve subscribed to them or not. (Contrary to some misconception you don’t need to subscribe to the people you put into a list.) Retweeting of such posts isn’t possible. These Lists only collect proper statements of these people, not their @-messages to others or RTs (exception: if a post is retweeted via an external client, the message prefixes a “RT”). One cannot address all members of a List collectively. Groups on the other hand are a kind of List you put yourself into. Messages can be sent to all members of the Group via a specific !-tag prefixed to the group-name (a finer granularity can be achieved when the !-tag is combined with #-tags. ) In a Group (contrary to a List) you cannot be put into by somebody else and then be written to (like on Facebook). Wheras on twitter you can create a great amount of Lists, on identica you can have a great amount of Groups. But in both, twitter as indentica, you only have one Personal Timeline in which to write.
6. Link-abbreviation : A very nice feature of identica, not to be found on twitter, is the built-in abbreviation for URLs. As 140 characters are a treasure anxiously to be guarded, one doesn’t want to waste them on redundant “http://www”-prefixes. So an address like “identi.ca” is as valid an URL in a post as “http://www.identi.ca”. (I didn’t check for “ftp” and “https”.) The same works for URL-shorteners, reducing the numbers of characters needed to form a clickable link still further. Sadly, twitter hasn’t adopted this terrific idea – in messages sent from identica to twitter such an abbreviated URL ceases to be a link. (One has to copy and paste it into the address-field of the browser to regain a working link.)
7. Switch off the RT : In twitter, not in identica, you have the means to switch off the RTs a person you’ve subscribed to sends around, thereby at times drastically reducing the number of tweets you receive from that person. Identica, due to reasons of “discovering“ communities, has no such option. 
8. Search : In identica one can search for people, notices, and groups, on twitter only for people and key words. (I don’t know whether there is an option to search specifically for lists.) Rather annoying in identica is that (when logged in) you cannot search for your own dents (beginning with your Avatar’s name) but only for messages of other people that include the seach phrase (and may or may not include your Avatar’s name and the phrase as well). This makes a backward search through your publication history very arduous. But this is still better than trying to search through your tweets on twitter: even as the search is possible, twitter cuts off search depth by restraint in time.
9. Subscribe to tags : This isn’t possible in either service but there are workarounds. On identica one can create an RSS-feed for a hashtag that can then be monitored by an RSS-reader.  In twitter one uses the search to create “lists” from keywords or hashtagged phrases that can be saved. They show up in the folder “Searches” and auto-update.
10. Save : In identica your past dents are always accessible to you (even in an laborious way), twitter on the other hand seems to delete tweets that are beyond the threshold of 3000 tweets. (At least that is the rumour I’ve heard. Perhaps it only means that twitter stores them but doesn’t make them available for search or backup.)
11. Delete account : Can be done on identica with an email to the admin of status.net. Deleting the account means every dent gets erased. This has impact on all the conversations in which they occur as their deletion breaks down the dependencies between the dents. On twitter I don’t know specifics besides that there is a way to cancel the account. Even if thereby the tweets would get erased too, this would only have a minor impact as the conversations on twitter via replies tend to be rather short and mostly involve only two persons.
All these features make identica – or rather its software StatusNet – a terrific tool for In-House-communication. A company, a project, an organization, a news-broadcaster, a civic administration, etc., can use this platform precisely because of the Group- and Nakedness-functions. One can organize teams around groups and delineate proper sub-groups via the combination of !– and #-tags in the messages. Or rather: one can specify the range of dispersion one’s message shall have. The feature Context gives (at least in principle) a spreadsheet with which everyone can have an overview about a conversation, its participants, and the concrete points of entry of messages to a given discussion. But of course groups don’t need to be real groups of people. Groups can be themes, topics, agendas, projects, deadlines, perspectives, discussions, etc. In short: the term “Group” can refer to assemblages of people, but decribes more accurately a specific content people contribute to or with the help of which they contribute.
Groups as well as Nakedness are key features of identica and, as I found, a major curse as well. Imagine you are part of a Group, say “linux,” that only has roughly 13.000 members. Imagine only a fraction of them dents messages to the Group with the “!linux”-tag. Can you envisage what quantity of messages will fill your Personal Timeline? Now imagine you have subscribed to some very nice and interesting persons who are denting around the clock. And given as they are interesting and nice people that they have many subscribers and subscribe to many. The result is that they will dent all day, send @-messages, replies, and RDs around the clock, all and everything of which lands in your Personal Timeline, especially stuff to people you don’t know, perhaps don’t even want to know, but that you cannot switch off.
Add to this that there are people who dent 20, 30, or 40 messages a day (the RDs not included). With just one Personal Timeline and without the means to reduce the number of messages, the Timeline gets overcrowed and the succession of dents will become very fast. (This may make it really hard to reply and enhances stress when you try to follow up in a conversation). Include the stuff coming from Groups and you’re in a position at which you start to become incurious to any content. Content becomes spam.
The problem of Content-Spam is of course not confined to identica. On twitter one may have a fast Personal Timeline as well due to the sheer number of people one has subscribed to. In both services there seem to be only two ways to deal with this input. The first is to stop reading every post and to react only to the ones that somehow stand out of the rapid stream. Seemingly, this is the way most people on both services deal with the incoming stuff. The second is to somehow reduce the mass of posts in the stream. Whereas the first strategy accepts and at times deliberately enhances the speed of the stream, thereby only surfing above the waves and tides the posts create, the second actually slows down the speed in order to absorb every note that comes in. I prefer the second. I don’t understand how people on identica and twitter who subscribe to 1.000 people and more can manage this. How do they read all the stuff and react to it? What kind of communication results with a dipping-into-the-stream approach? For me this way is not an option.
The only means I found on identica and on twitter in order to cope with the huge amount of messages was this: Firstly, I reduced the number of subscriptions (whom I subscribed to) to about 30 people. Secondly, I came to subscribe only to people with the average of seven dents a day. (Identica lists the average number on the people’s Profile- and Personal Timeline-pages.) Thirdly, besides choosing people via their interests, tone, wit, etc., I subscribed with regard to their favorites and RDs / RTs. The quality of the RTs (or better: their importance to me) is a helpful way to alleviate the need to subscribe to other people as well. (The interesting stuff will get through, as the news will reach me anyway.)
But on identica I have no means to put “heavy-denters” in a List that could act as “suggestions for further readings.” Accordingly, I couldn’t follow on a regular basis what these people were writing. (My workaround was to bookmark their Profile-page in order to have a quick glance over their last 20 or so dents.) I guess, some of them who had subscribed to me were wondering why I seemed to be “dismissive” about subscribing in return. In fact I wasn’t at all, I would have liked to but I wouldn’t have been able to cope with a dent-tsunami. So sporadic conversations took place only when they sent @-messages or direct replies to me. These showed up in my Personal Timeline.
Group, Nakedness, and Context are features in identica that are magnificent if your overall pool of participants has a definite boundary to an outside world (usually provided by the topic that helps to separate the spheres.) But as soon as you use them as means for open, unrestricted, and unorganized gatherings of people, the only way to cope with a tsunami of content is to filter on your personal side. That doesn’t mean to turn a blind eye on this or that, but more specifically to treat the stream as a stream of statements, status-reports, data, not as something persons have crafted.
Form determines function
I’ve always wondered why identica is such a geek-biotop. Or rather: a monoculture full of geekish themes like programming, Linux, distros, Windows-/Apple-bashing, FLOSS, Creative Commons, etc. You don’t find a thriving art scene on identica, nor a thriving micropoetry-scene. No history, no social speculations. Activism, yes, Hacktivism, in a sense, but a nice chat about a film, a ballet, a book? Gardening tips? Stuff about parenting and children? Women’s Lib? Men’s Movement? Health, medicine, tax evasion? Of course, on twitter one doesn’t find this either in form of lists or clear-cut conversations but at most as subscription based conversations between individual people you have to be lucky to stumble upon. But the differences between both platforms are still striking. As identica allows for conversation, to and fro, twitter only (or mainly) allows for single statements, much less for conversations through tweet and reply. And my suspicion reaches even further: The features that make identica/StatusNet a magnificent tool for In-House-communication are exactly the ones that drive away every communication or exchange that is less than agenda-driven.
If this is true, and it’s primarily a supposition, not an evidence-based observation, then two of the main explanations I’ve heard of why there are only geek-themes on identica seem rather misguided: The one says that identica is a geek-biotop because it is a young service, was started by geeks, and has only a fraction of the participants twitter has, thereby reducing the themes available and discussed intensely. The other states that everyone can come up with his own themes and is free to post on topics as he wishes. Both lines of thought are related, and I feel, both are more or less false.
Due to the limitations of 140 characters twitter as well as identica are suited for short, clear statements. (Clarity, by the way, is not a function of simplicity, but of patience.) Thoughts longer than this have to be rephrased, shortened, and/or redacted to fit the (nowadays arbitrary) restriction in characters. This not only makes longer discussions and the response to different points of view arduous. The longer a discussions gets the more complex arguments and reasoning tend to become (not the other way around). Referring to all those aspects within still 140 characters is not possible. (I’ve read very often a reply stating somewhat like “I cannot discusss this further within the limits of 140 characters.”) What a discussion on identica looks like to be in order to fit this limitation is a succession of pointed rebuttals, one-liners, sharp phrases. You win the argument if you have the last line in the conversation. You are right and your position is true if you can defend it against all attempts of rebuttal. Of course, refuting rebuttals will not make your proposition true, it will only show that you are a smart ass and are capable of fending off an attack. Accordingly, screaming becomes the norm. Social media tend to become scream media.
Not that this is all unreasonable behaviour. Identica was created and is primarily used by geeks. Even if they are not all mathematicans, physicists, computer scientists, etc., there is a bias for argument (indirect proof, reductio ad absurdum) and succinct formulation, all good and nice things. The nerds on identica form a huge Meta-Group (the one the members of which use !-tags and #-tags to further divide the assemblage) due to their themes, styles of conversation, and common technical interests. For them statements are about facts (reliable or disputable), those facts have clear boundaries and topics. Data and information fit in neatly.
But for people like poets, artists, etc., topics and their expression are of a rather different kind. People from the humanities, from literature, the arts, sometimes even the social sciences, often wrestle with the problem of finding the appropriate form of or expression for a thought. For them, thoughts are rarely that verbal, they don’t consist that much of data, contents, information. They struggle with differences, borders, shades, metaphors, and with ideas whimsically grinning from the back of their heads (or wherever else). To put such stuff into words is often hard enough but to put it into 140 characters can drive you mad. So even if the only analogon to a geek’s statement are bonmots, aperçus, micropoetry, it’s rather hard to get at them.
One writes what creates responses. The atmosphere on identica “pushes” a non-geek to write in this prevalent fact-stating, nonchalant manner. The poet, thereby, becomes a geek – at least in manner and style, wondering why his themes and interests begin to elude him. Given the conversations that take place on identica, a poet or any other non-geek will begin to feel rather out of place, and the geekish atmosphere will in effect create a feedback loop enforcing this stance. Compared to this twitter’s absence of communication or discussions (due to its different functionalities) does less “harm” to the poet. People can state their issues without having to enter debates, that due to the design are difficult to continue beyond several steps. With lack of discussions it allows the haiku-poet to sit in his corner, chew his pencil, mumble, and count his syllables. There is, in a strange sense, some calm and privacy on twitter that identica lacks. “Open” isn’t always something to be cherished.
Statements about vague or filigree topics are difficult to formulate within the restriction of 140 characters. It’s no wonder that mainly micropoetry became a blooming non-geekish genre on micro-blogging platforms. It combines character restriction and filigree topic in a statement. Accordingly, you can use the words similar to the geeks but with a different goal and ambition.
But on identica (as opposed to twitter) one doesn’t have lists that may serve as “suggestions for further readings.” One only has this one Personal Timeline, and given all the features identica uses to foster disucssions it will be cluttered with stuff not relevant to what one is working on right now. Additional to that the rather rough and honest tone that is prevalent on identica (and that I much cherish and miss) may push some thin-skinned people away who are more in vagueness and hoity-toity. But given one has survived all this and starts to post about “one’s own topics,” there is nobody there who listens. Some day, those five or six interested people will have found each others, dent and redent each other, and recognize that neither collaboration nor prolonged chatter gets started. Not that twitter has much collaboration either, but a reciprocal valuation of one’s new haiku, a friendly greeting, the notorious rounds of thank-yous for the last RTs one has received does something different – it creates atmosphere. While for geeks agenda, common interests and content help foster community, for poets it’s rather appreciation, a nod, a slight touch of recognition. Content, for the poet, doesn’t foster community; it’s the strenght and depth of the community that decides what content he is going to post. (As nearly nobody posts personal stuff on a “social” medium.) On identica the means to create bonds of interests are much weaker than on twitter as identica’s design accentuates the direct engagement with verbal content, not the building of atmospheres the non-geek often needs to get “started”. To put it simplistic: The design of identica is suited for finding and creating communities, but not for fostering and curating them.
Identica lacks a lot of topics that are not directly connected with IT-stuff: Political activism, human rights, women’s lib, ecology, indigenous issues, etc. A good part of it could have a place in identica but it’s a place for those interested in technology and programming. Artists could to a degree use features like Groups and Context, but don’t do it. There is no point for them to come to identica. With 140 character limitation you cannot start a throrough discussion on filigree topics anyway. You won’t do. As identica promises more than twitter, the disappointment concerning its usability is much stronger. Micro-blogging sites, as it shows, reduce conversations to the barter of statements. In that, they are, in a sense, profoundly anti-social and the opposite of a conversation.  So leave a message. I call you back.
 ∧ It’s often the historical knowledge of how a software, a concept, a tool evolved that leads to applause, not the actual benefits or accomplishments a unsophisticated user may gain.
 ∧ This important design feature was highlighted by @chicafrikki in her very recommendable post Twitter vs. Identi.ca. O ¿Por qué Identi.ca es mejor que Twitter? (in Spanish). (The vibrant Spanish speaking CC-/FLOSS-/Linux-/Social Media-community is a very good reason to learn some Spanish, folks!)
 ∧ This seems to change as StatusNet is working on “Privacy“-modes, i.e. a “limited distribution,“ that allows to hide and send “private“ messages to subscribers. Cf. http://ur1.ca/3pe5s and http://ur1.ca/3oxdm .
 ∧ The remark that this makes identica far more like a chat is an oberservation by @chicafrikki, see .
 ∧ Cf. the conversation involving @support of identica at http://ur1.ca/3pe7r .
 ∧ Private conversation with @brightbyte , thanks for this suggestion.
 ∧ That conversations are no barters of statements cf. e.g. my post Dancing a Thought.
In a follow up to this post – A Wishlist For Identica – I list a few features and things I’ve missed in identica (and in part in twitter as well).
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