I don't understand why Quora seems to be a standard to some. It hides it's answers behind a registration wall and ask that you give it access to your Facebook profile on registration.
Not to mention quietly setting up a public profile page in your name that starts showing up among top results when people search for you. Creepy is right.
A lot of website use appeals when it has a local flavor. Quora and it's Silicon Valley answerers probably doesn't know how to answer the questions that many Non-US citizens might have. This has a lot to do with user base, and I don't see Quora marketing itself outside of America.