What about an UI which mimic a social network in the Facebook style but which uses email as backend? It would be decentralized for free, and entirely interopera

What about an UI which mimic a social network in the Facebook style but which uses email as backend? It would be decentralized for free, and entirely interoperable with people using plain email (those who uses this UI would see that you liked there message, others would see a reply that says "I liked your email", for instance). Comments would be responses to email (using the In-reply-to header). The interface could easily creates groups of contact or post to all of them (equivalent to posting on your "wall"), etc. The action of "friending" someone on this UI could optionally be mutual GPG key signing behind the scene which would enable encryption of messages between friends. I think there is a lot to do with this idea.