There are of-course grey areas, but the key is the community. They don't optimize it for "where do I ask the question?". You could probably ask it in Yahoo answ

There are of-course grey areas, but the key is the community. They don't optimize it for "where do I ask the question?". You could probably ask it in Yahoo answers or Mahalo then, that pretend to answer it all in one place. Or Quora. The key is to create a community of people with common interest, where there is enough interest (Area 51) and have them connected. Getting answers is a side effect. They have nailed this part and you have to give it to them. For what it is worth, questions that doesn't belong in a site are automatically, and generally quickly moved.