Russell Beattie did it as well, but also played with the opensource code that powers identi.ca, and found some very basic scalability issues. The comments are worth a read: should a microblogging service be considered as a messaging system like SMTP or Jabber, or as a content management tool like blogs. Each approach has its pros and cons.
The messaging approach can have issues with message duplication for highly connected people, whereas the content management approach requires expensive queries to aggregate posts from people you're connected to.
Laconi.ca (the software behind identi.ca) aims at solving this by allowing microblogging services to be federated. Not sure this will actually solve the scaling issue as it moves the problem from scaling the internal database/messaging system to scaling the federation aggregator.
Allowing federated and interoperable microblogging is very interesting however, since it gives us choice and freedom: you can do your microblogging where you want, and not where everybody is.
Next step will be federated social networks, where you can choose the one that best suits your needs while still being able to connect to people that are elsewhere. OpenSocial could be a way to achieve that, although it concentrates today on interoberability of widgets among containers and does not (yet?) address interaction between containers.
Lots of interesting subjects to work on for Goojet. But also so much to do :-)