I sometimes go to http://voat.Co and poke around when I want to remember what the Internet used to be like. It's one of the few forums that doesn't have a blanket ban on expressing anger.
What's funny is that it's very Californian to never express anger. East coast culture is more direct. People will say to each other that they don't like something the other person did or are upset or angry at the other person. On the west coast, especially California, it's really important to be nice, so people will just cut off contact when they've been offended or decided they don't like someone rather than confront them. Those California social values seem to have migrated online.
I think they've still got at least another year or two before this becomes really obvious to the mainstream, but Facebook is definitely headed in a dangerous direction right now. Not to culture; it will survive. It can't be killed even if you want to kill it. (You can hurt it, but not kill it.) But to Facebook. The appeal of a space where you can't say anything that is negative that might be associated with Facebook isn't great to start with, but when you realize that it's Facebook that has sole control over what it considers negative you also get that helpless feeling. Most people aren't going to analyze this... they're just going to realize they don't feel good when they use Facebook, either because their posts are getting censored or because they are subconsciously self-censoring, and operant conditioning will lead them away.
It's becoming more obvious every week that Facebook's instinctive reaction to everything is to control it with a heavy hand.