I completely agree about the anonymity. That is really the core of 4chan and what I find appealing about it. Everything that is said there is for the sake of the thing being said and not about building yourself up as a persona.

There needs to be other sites that don't have usernames in any way. Even if you attempt to ignore it, it somehow is always relevant. Somewhere such as Reddit in particular always comes down to being a popularity contest and it will skew what people are willing to say in order to get the most likes.