It all depends on what you mean by “worst.”
Sites like SodaHead and Reddit have very little censorship (which is a good thing, IMO), but that means that there’s a lot of mean, nasty, hurtful content there.
If you want to be insulated from having your feelings hurt (but sometimes have your comments moderated [that you think are helpful and on topic] because sometimes a moderator comes along and interprets the rules a little too strictly), then there are sites like Fluther and BlurTit.
Both styles are useful and fun and contribute a lot to the web community in their own way.