Paul Graham has an interesting post on forum & blog trolls where he explains the factors he thinks contributes to rude behavior by members. Anonymity plays a role, but so does the forum’s acceptable culture:
The final contributing factor is the culture of the forum. Trolls are like children (many are children) in that they’re capable of a wide range of behavior depending on what they think will be tolerated. In a place where rudeness isn’t tolerated, most can be polite. But vice versa as well.
I don’t know if children is the best term for trolls since that would imply that moderators are like parents. I think moderators are more like bouncers who keep things under control and kick out people who are behaving badly.
There’s a sort of Gresham’s Law of trolls: trolls are willing to use a forum with a lot of thoughtful people in it, but thoughtful people aren’t willing to use a forum with a lot of trolls in it. Which means that once trolling takes hold, it tends to become the dominant culture.
That’s dead on. Why would anyone leave a thoughtful comment on a YouTube video or Digg post if it’s just going to be buried alongside all the rudeness? We see a bit of this locally on the occasional degraded MNSpeak thread (although it’s not consistently crappy like YouTube or Digg comments).