I think most of these online communities are following a very simple pattern. And the cycle of a typical message board is sort of a microcosm of Reddit. Message boards sometimes struggle for users at first, inviting people in, having fun events and making the early users mods or important members of the virtual street team. For a time, this works. After the board gets going, the community grows. As it is growing, people tend to be positive, whether they are "negative people" or naturally "positive people" because a growing message board is popular and to fight popularity on the Internet is hard. The natural tendency is to go with the flow.

But somewhere between the site growing and the site becoming too crowded with users is a tipping point. It begins slow at first. Someone takes a comment the wrong way, gets upset and then apologizes. Then maybe an argument erupts. Grows and then fizzles out. Each tiny event adds up and the hardcore visitors begin to worry about the board. They take it upon themselves to help bring in people, teach them and avoid problems and arguments, but as people have said on this site, it just isn't possible.

Eventually, someone rolls onto the site boiling over with emotion and bad reactions to everything. Whether it's a sarcastic user cutting everyone down because he's become bored with the post or a disillusioned early user who feels threatened now that the board is popular. Actions turn into reaction and then into reaction again. Now some boards might have really on-the-ball mods for a time, but we all know these volunteers fade, leave or just stop caring. The trolls eventually snowball and the board soon becomes a place where you have to watch what you type, lest you get insults, attacked or banned. This drives away the lurkers, already shy about posting, then new people and then eventually the trend pushes people away from the board until it either dies or gets revamped.

Reddit has gone through all these phases and now faces another revamp. But revamping a site like Reddit is like trying to restart a really cool conversation that devolved into an argument. You're better off just starting over. The new sites aren't full of drama yet. They don't have Reddit's baggage, even if they eventually head down the same exact path.

I don't believe there's anything that can stop this process, save keeping the community small, but that flies in the face of the business model. And size is relative to the site and its popularity. There is no way to keep out trolls or get rid of them before they do damage. There will always be jerks and there will always be naïve people that get sucked into their drama. You simply abandon that poison well, start fresh and keep an eye out for the next well.