It's interesting that you mention traffic from search results. I do a lot of queries, on a lot of topics, some of which Quora could probably give me an answer to, and I have never, ever, seen a Quora question appear in Google's results. Until I checked, I actually thought Google didn't index them (it does, but I only see it when I put "Quora" in the query, which kind of defeats the purpose).

Could be due to a lot of things (location, Google bubbling me, etc) but frankly, if that's what they rely on, I feel they have a long way to go. They are very far behind Wikipedia or Stack Overflow, for that purpose (even if those aren't their most direct competitors).