This article was written before “New Twitter” was launched, but I believe most of it still stands. It has been slightly update in September 2011 to include a few evolutions, but is mostly left untouched.
[Note: this is a self-translation of a French post I wrote a little while ago. I don't like self-translating, it makes stuff sound less natural. Hopefully this will turn out ok, otherwise I know who to blame.]
Let's immediately agree on the obvious question: Why would anyone use Identi.ca when everyone is on Twitter?
Basically, this is the same question as “Why use Diaspora when everyone is on Facebook?”, “Why use Facebook when everyone is on MySpace?”, “Why use MySpace when everyone is on Friendster?”, or the good old “Why use XMPP when everyone is on MSN?” and “Why use MSN when everyone is on ICQ?”.
By now, I think most of you see where I'm going with this…
There is always a network that is more popular than others at a given point
in time, without it being an obvious guarantee of said network's quality.
This is simply the case because a network's value is equal to its number of
users squared. This is called Metcalfe's Law.
In our case, “everyone is on Twitter” clearly gives superior value to
Twitter.
Of course, “everyone” almost always really means “everyone that is actually
interested in this service at this point in time”. Even Facebook, gargantuan
monster of a social network that it is, can not (yet?) claim to be a universal
address book.

