SMOB is a prototype developed to enable semantic microblogging. It can be seen as Twitter enriched with semantic data.
John Breslin writes in his blog post:
The prototype uses FOAF and SIOC to model microbloggers, their properties, account and service information, and the microblog updates that users create. A multitude of publishing services can ping one or a set of aggregating servers as selected by each user, and it is important to note that users retain control of their own data through self hosting.
I think it is an interesting prototype whith future perspectives in the semantic web. Check out the SMOB Project Website for more information.