Two observations about user behavior in forum settings
When attempting to enforce real name policies in online foras discussions tend to get dumber.
I guess because real name policies work better against smart and nice people than against trolls.
When accounts are short lived or ephemeral discussions seem to get less civilized
I also wonder if, just like how people in nice cars on average seem to behave badly more often, people who have little to fear (powerful, has correct opinion) has a tendency to behave badly online more often. But I don't have data (yet at least).