Raph Koster has a great writeup of The Trust Spectrum, which is a design framework he worked on in collaboration with Google’s ATAP group and Aaron Cammarata. It examines how we build (and break) trust in games, though you could extend a lot the examinations of trust to community in general (which is sort of the point: the goal was to see how we could better build social connection in games).
It’s a good read, in particular if you’re remotely interested in game design, online communities, and online games. (In a similar vein – and mentioned in Raph’s article – is Dan Cook’s article, Game Design Patterns for Building Friendships, which is also worth the read.)