...is to provide security for those making a statement. This works for the speaker no matter what the comment. The effect on society depends on what the comment is. If that anonymity is protecting a total slimeball making racial or other slurs, then it's bad. If it's a factual comment and that anonymity is protecting the commenter from retaliation from whoever he commented on, then it's a good thing. To update the old saying: "It's better for 10 guilty people go free than 1 innocent jailed", to "It's better to tolerate 10 idiots than silence one whistle-blower."

The issue is not anonymity, it's the social compass of the posters. Somewhere, people decided that the anonymity allowed them to let their slimeball side run free, instead of imposing self control and posting responsibly. We need to address the reasons behind why people feel that they need to make posts like that. Unfortunately, repeated education cuts rather points to the problem.