Or Twitter, I think. But yes, it's a very odd choice to not allow (1) OpenID logins, and (2) basic registration - particularly given their early adopter audience.
Maybe they don't allow it because of their early adopter audience: who among that crowd does not have a twitter or FB account?
I'm obviously not an early adopter :) Actually, in seriousness I'm probably not. But still, I like to remain anonymous and only reveal personal data when I have absolute control and trust in over who/where I am releasing it to (and I don't mean I don't trust Quora, it's exposing myself to their users that I have an issue with)
I didn't like Quora at all. It allows users to modify your question and tags and some of them misunderstand your question or just don't want it there. One of my questions received no answers, many followers hoping for an answer, and 13 edits removing tags and changing the question to be something completely different from what it was. In other words, it can be abused.