It was only two years ago that microblogging services like Twitter and Jaiku came on the scene, and in the last year, use of them has accelerated and become a cornerstone of communication for many. The popularity of this emerging model has spawned many derivative services. Most of them aren't interesting enough to warrant a post, but identi.ca is, and not just because it comes out of Montreal from Contrôlez-Vous, Inc. (Control Yourself, Inc.).
On the surface, identi.ca differs little from Twitter, retaining a simple layout and 140 character messages. The difference is under the hood. With Twitter's rapid growth leading to frequent problems and downtime, it seems clear that a decentralization is needed to reliably scale microblogging. The world doesn't depend on one email service, why should Twitter be expected to carry the weight of the world's micro-communication? Identi.ca solves this by being the first service to implement the OpenMicroBlogging standard for publishing notices between services.
Further, Control Yourself has open sourced identi.ca in the form of Laconica, a PHP app. Montreal Tech Watch theorizes that Laconica could become "the WordPress of microblogging platforms", as anyone could use Laconica to set up their own public or private site capable of exchanging notices with identi.ca and other OpenMicroBlogging sites.
These are early days for open microblogging. The standard is only at version 0.1, and it hasn't been adopted by any of the big players yet. With this launch, Control Yourself has put forth some good answers for how to solve microblog scaling problems, and to bring our micro-communication out of walled gardens.
Final thought: There has to be a better term for this communication model than "microblogging". "Micro" makes sense, but my observation is that people tend to use it more like an IRC channel than a blog. If you have a better suggestion for an alternate term, please post in the comments to claim the attribution as your own.