I don't know much about Quora, and have never used it, so I can't comment on its chances of success.

But I really don't like the name, and I think it may hold them back, as far as mainstream adoption goes. It's not an attractive name to begin with, and I don't quite know how to pronounce it: koo aura or kwaura (rhymes with Laura)?

If we're comparing Quora to Facebook and Twitter, it loses the name game by a mile. Facebook and Twitter are both easy to say and there's no confusion on spelling or pronunciation. Also, Quora can't be easily or obviously verb-ized; "Facebook me" or "Tweet it". I don't see "Quoraize it" or "Quoing" becoming a commonly used phrase.

All of this may be irrelevant if Quora is just that good, but it's certainly something to think about.