This is a situation that has been bothering me for a long time.
It happens in a lot of sites, but I'll use digg as an example.
Someone posted a story about some school in Canada prohibiting the use of Wi-Fi because the director thought it could be dangerous to children's health.
Now, that's ok if you find it completely absurd. It probably is.
But what surprised me was the content of the 100+ comments about the story. More than half of them were, putting in 'nice words', about how Canadians are stupid, how something like that could only happen in a 'lame' country like that, and it goes downhill from there.
Same thing about when someone posts in a popular weblog like joystiq.com about some Playstation 3 news. Lots of comments are 'flames', like 'Playstation sux XBOX 360 ROXXORS' and the same goes for any other consoles, or Macintosh and Windows articles in so many other blogs / digg-like websites. That's no different in my country's (Brazil) websites, forums, et cetera.
I can say for myself that I have never wrote anything in the net that I would not say to a person's face (Ok, 11 years ago when I discovered the net and was 17 years old I did some flaming in chat rooms - remember when these were popular? - but after 1 month or so I saw it was not the kind of fun I liked).
All the hate in the Internet just astounds me.