Brainstorm!

Prompted by a discussion with bunnykitteh, who's good at prompting these kinds of things:

Imagine a Facebook and/or MySpace application aimed at organising flash mobs for political action (e.g., the kind of thing Anonymous might use to quickly notify members of imminent $cientology activity in a particular location). What features should it have? (Twitter gateway?)

(Note that with Facebook, especially, there are all kinds of interesting concerns with respect to privacy...)