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.
Yeah, I think you could combine a number of existing services to make a network- email, twitter, HN, github, a linking service (this github profile = this twitter account) and an address book service would get you going for a dev network. The challenge would be to combine the data meaningfully, but I think the basics can be done. Plus, your address book amd email could be private services.
