Reminds me a bit of bars/clubs. They're often either dead, overrun with idiots, or at the sweet spot. Commonly, that sweet spot is in the early stages when the place is still novel and cool but yet to be discovered by the meat-market masses.

Maybe the early adopters have some contact and relationship with the bar/site owner, so they treat the place with a reasonable amount of respect. As that contact diminishes, hordes with no interest in preserving the community dominate. In bars, they damage things or start fights. Online, they troll and abuse, pushing the more reasonable types away.