The preview.

And as others have said, if it's not on Google, how are you going to find the site in the first place? For a Q&A site that really needs to start turning a profit, this is not a trivial issue.

Quora is on Google, and ranks really well on Google for long tail keywords despite the everything but the first answer not being included in Google's index (blurred out). As a matter of fact, I've even gotten a client who came from Google after finding one of my answers.

I know HN loves Quora links, so: http://www.quora.com/How-is-Quoras-SEO-so-damn-good