Except if your internet goes down. Which happens to me often enough that I only really pay for my service 8 months out of the year, the rest being comp'd. Gotta love Cablevision. Also, what happens if/when, for whatever reason, your node gets a flood of traffic? It can kill all your bandwidth, since most people in the US don't have that much to begin with. And most people would not think to pull the plug (heh pun) if that were to happen, rather they would blame it on the ISP, I'd think.

But it's certainly a cool thought. I'd be more interested in it being used for P2P file sharing, but restricted to friends. Like wirehog.

EDIT: It dawned on me that file sharing would take up a ton more bandwidth than 99% of social networking. In either case, I suppose some software limits could be set to throttle requests.