How has Perlmonks managed build a useful, cohesive community when so many other "community" sites have failed, either by fizzling out or imploding. What's special about this place? What dynamics keep this place special (or even workable)?
If you're of a mind to puzzle over questions like these, I highly recommend a recent essay by Clay Shirky, titled A Group Is Its Own Worst Enemy. There, Shirky talks about some non-obvious aspects of group dynamics, and then shows how on-line communities either adapt to group dynamics or don't.
Without giving anything away, Perlmonks does a bunch of stuff right.
Go. Read. Ponder. There's some good stuff there that we'll get back to later.