OK, I didn't express myself well. Let me try again.<p>I didn't mean that StackOverflow is like it is because of the career site. I don't know why it became successful. 
My main point is that people ask stuff there because it actually helps them do their job. This means:<p>1) Vague, badly written questions and do-my-homework requests are frowned upon.
2) It's a service that people would potentially pay for.<p>In contrast, on places like Yahoo Answers people ask all sorts of random questions and get an accordingly wide range of answers.<p>It might be that regardless of the professional nature, programming provides a higher barrier of entry than language study.<p>That's why I thought it would be good to market it to translators.