I'm thinking of doing a PhD on "A Model for Online Collaborative Software using Reputation, Attention and Trust." If you look at successful sites such as MySpace, SlashDot, or Digg I think they depend on a model of RAT. I've been using online communications since 1979 so feel I can make a contribution. A really good roundup of Reputation and Trust can found here. Adding Attention might mean a gap and an interesting model.