StackOverflow benefits from two things: 1) started by Fog Software who has a reputation, and 2) there's a natural filter in place with its content. Perhaps just perception bias but I think it helps weed out an overload of questions like "how can i get listed on search engines".

At some point there needs to be moderation to maintain quality and define the scope of the site, otherwise I think it will struggle to have merit, IMO. The first question I clicked on is regarding "social media" by a hotel owner. Certainly a valid question but how is this related to startups? Are you assuming that any business getting started = startups?

http://startups.com/questions/1447/how-can-i-define-my-strat...