I’ve taken great delight in applying Peck’s 4 stage model of community to dozens of communities. To use a familiar example: Triiibes.
Seth Godin’s Triiibes is an excellent example of how communities develop
Pseudo-Community: First members joined and were extremely polite and feigned enthusiasm for everything (secretly, most members wanted to impress Seth).
Chaos: Then conflicts began to happen. Member's, once comfortable with each other, didn't feel the need to hide their own ego or ambitions for the benefit of the group. There were some good fights, some members left.
Emptiness: Then the community was a bit aimless for a while. Gradually, however, members began to communicate better, developed a group tone/voice and put their own agendas and egos behind them.
True Community: Now Triiibes is a very productive community. One that has written two ebooks, succeeded in getting a member to speak at TED and racked up an array of productive (and unproductive) discussions.
If you want to develop your online community, it's vital you take them through this process of development. Don't try to resolve or prevent conflicts too quickly.
Also, closing your community for months at a time can be a very good idea. Taking a fixed group through the community process can be easier than handling hundreds of members at different stages.