Quora begins making money with the introduction of advertising

They made a great big splash when the media genuflected to the idea that "You can ask a question about Facebook, and Mark Zuckerberg could answer!" So regardless of the question or answer there will always be dominance by celebrities and their celebrators gleefully upvoting anything they post regardless of underlying fact.

I prefer Stack Exchange. The site is less about being the best person to answer and more about the answer itself. There is far less correlation the number of fans a given user has to their number of up votes and likeliness to be accepted by OP as correct or most helpful. I find real discussion occurs when we lose our preoccupations with who we are and focus on the subject matter instead.

Not everything has to be a business though. Quora (in my mind, at least) would be good in a distributed/federal setup, as would twitter.