Max Goldberg, the creator of YTMND, has this to say:

"I'm straying off topic, but the point is, the users are what make YTMND. Crappy users make the site crappy, and rather than trying to delete crappy content, it would be far easier to just keep users who create crappy content off YTMND. The hard part is figuring out who to let in and who will add value to the community and the site as a whole. "

Well, sort of true:

http://ycombinator.com/announcingnews.html

Yes, because of reddit. Yes, because of Arc. But mostly because it's a good way to learn about people.

That group enemy link is really insightful. Mod parent up :)