People.
I never read the comments anymore. They make me angry.
Same here, I try not to as well. Sometimes when it's in an unusual place (like a technology forum!) my curiosity gets the better of me though, DOH! But people are the same everywhere, unfortunately! 
The constant bleating about tax avoidance is the one that gets me, but it just shows their ignorance of not only the issues at hand, but the strategies that he advocates. But I really can't be bothered pointing out the flaws in their rants, after all, if they take the time out of their day to slag off Bono on some news site, I don't think they're the type that will be persuaded by truth, logic and reason.