Quora is interesting; StackOverflow is important.

Lately, though, Joel, his partner Jeff Atwood, and the StackOverflow community have spun off dozens of other Q&A sites under the “StackExchange” umbrella, in an attempt to beat Quora and the like at their own game. And are they ever screwing up. Their policy is to spin off new sites built around themes suggested and approved by their existing community. So what do you get as spinoffs from a coder community? A bunch of StackOverflow subsets for super users, sysadmins, etc., and a hodgepodge of sites focused on photography, mathematics, Apple, video games, board games, role-playing games, and science fiction. Interesting? Sure. Important? Hell, no.