Something like this doesn't NEED to work "ontop of" email though. It just needs to work LIKE email, and be decentralized, where anyone can run a "facebook like" social networking server that all know how to talk to eachother. I certainly do applaud efforts like Diaspora. If only they could actually take off. Maybe this approach of working "on top of" the existing email infrastructure will help adoption, IDK. But It seems like it will be equally as challenging to make popular. Might as well write a new protocol that is simply similar in its decentralized nature, so we dont have these issues.