Ari Kohen finds them wanting:
There’s something freeing, to be sure, about being able to say anything you want. You can engage in unfounded name-calling, or intentionally hurt someone’s feelings, or just generally behave like a twelve year old. And no one will know it’s you. And that’s why I don’t read many blogs that are written by people who prefer to remain anonymous or who write under pseudonyms when there isn’t really any reason for them to do so. In fact, I don’t think there are any blogs I read on a daily basis whose authors are anonymous. The anonymous or pseudonymous blogs are often just filled with cruelty, name-calling, and bad arguments. Indeed, there are a great many people who choose to write under an assumed name because they want to harrass or offend others.
But there are others who produce great stuff. Pseudonyms have a long history in political discourse, and I think they have their place. If they launch ad hominems, they're cowardly and will lose readers. But if they're a way to think out loud without any consequences in your other, say, professional life, I tend to agree with the wonderfully named Luke Simulacrum:
We’ve created a space where you can actually think and be different, be free of the norms, hierarchies and prohibitions of the “real” world, and be able to imagine alternative horizons of possibility. If you would really be willing to undo all of that just to prevent people from calling each other names on a comment board, you should really take a look at your priorities.
The Dish 