As developer of a Twitter application for Windows Mobile devices, I wholeheartedly understand that the web is fickle and that Twitter may go by the wayside for something better (like Google Wave, possibly), and that the consolidation of the Twitter platform is counter-productive to the open, non-centralized nature of the Internet. However, I do have to mention that the platform that Identi.ca is based on, Laconi.ca (now known as Status.net) does work in a manner similar to Wordpress – you can have your own hosted solution or “roll your own server.” What’s more is that it supports “remote subscriptions” (http://status.net/wiki/Remote_subscriptions), allowing you to subscribe to other users that do not reside on your own server.
Twitter, however, has a huge contender coming soon in the form of Google Wave, and it may spell its doom since it too already has built-in support for “federated servers.” But the real question is this: will it have widespread support as Twitter does? These are important questions since this is why Twitter took off – you could use it virtually anywhere and in virtually any way.
So, although making a business solely reliant on Twitter is, yes, a little fool-hearty, but the platforms are out there that may make Twitter-like microblogging platforms as ubiquitous as DNS.
So, it isn't without saying that I believe that microblogging, like the regular style blogging before it, and journaling before that, will continue to live throughout the lifetime of the Internet, though it may undergo many different changes.