I'm amazed so few people are mentioning comments. 8/ I HATE getting Youtube comments. It's like the main requirement of posting there is do hand over your brain at the door. No one types decently, half the questions asked are answered IN THE VIDEO or IN THE DESCRIPTION, and my biggest pet peeve? When people swear at me because I didn't put up a video with subtitles and they can't understand Japanese. Nevermind that there are like 20 versions with the subs. <_<
But really, I dread getting comment emails in my inbox. Everything else about Youtube I can deal with.
And to all those whining about copyright enforcement? You are aware that it's illegal to upload copyrighted content anyway, right? :| I bet if any of you created a successful TV series or the like, you'd enforce your copyrights too. (And likewise, if you were threatened with multimillion dollar lawsuits, you'd remove the content right away, wouldn't you? D;)