What makes groups thrive?

I recently joined a group, and I am wondering about what makes a group work. The group is made up of some people who are quite a bit more conservative than I am (socially, politically). This bothers me a bit, and I am thinking about quitting the group and maybe finding a group made up of more like-minded people. But then, I recall reading an essay by John Perry Barlow (for more info on this EFF guy, click here http://homes.eff.org/~barlow/), in which he claims that the communes of the '60s failed because they were not diverse enough. He goes on to claim that a community needs dissensus (as opposed to only consensus) to thrive.

So then I think, maybe I should not quit this group but instead bask in the dissensus. I'll figure out my own group membership thing, but tell me what you think about the nature of groups and what makes them survive.