I don't think StackOverflow is really trying to be a general, mainstream Q&A site, largely because there is no mainstream when it comes to Q&A sites. When you g

I don't think StackOverflow is really trying to be a general, mainstream Q&A site, largely because there is no mainstream when it comes to Q&A sites. When you go to one of these sites, you don't want your question to be answered by a generalist, you want a specialist with domain knowledge to answer your question. Looking at it that way, the StackExchange model makes sense. Make a number of very specialized communities that experts can congregate in. Make a points system that rewards experts for their time and effort. Finally, invest in making the site friendly to search engines, so that non-experts can find the experts and ask questions of them.