I think part of the problem you're perceiving is that the examples that come to mind for"web community"--reddit, digg, slashdot, something awful, kuro5hin, sensibleerection, .+chan, etc.--carry inherent bias and groupthink: in learning to overcome bias, they best serve as sources of what to avoid.

This site does, perhaps, better than any other non-dictatorial group at keeping discussion rational: even groups of open-source developers working toward a common goal often devolve into chaos if there's not a single, strong personality in charge.

I'm not sure what the optimal solutions are, but if the hypothesized OB community doesn't reach at least the very high bar set here, I wouldn't have much interest.