The magic of Facebook, Twitter, etc are not the technologies. Sure, as they grow, they need more elegant than off-the-shelf solutions. But hacking together a Twitter clone in a week is the easy part - getting people to use it, building a community, etc, is the hard part.

The hardest part is that once your Twitter clone functions well enough to replace Twitter it will be banned just the same.

Unless I can do it sans central server, web torrent maybe? Any ideas?

The only effective solution I can think of is Tor, but then you automatically lose probably >99% of users. Everything else can be blocked easily.