I agree it works well on stackoverflow. However on this forum the questions aren't very specific so there usually are many correct answers to a question.
As someone searching for a code snippet to explain how to do something, the stackoverflow system is great.
However, my experience with it from the perspective of someone asking a non-trivial question is terrible (i.e. a question where you couldn't find the answer yourself by trawling through the API documentation).
Firstly there was a pissing match between mods, because one who clearly english wasn't their first language decided they would correct my question to their interpretation of the english language (i.e. mangle a perfectly structured sentence) and the other mod took exception to that.
Then some other chap who clearly didn't have a very deep understanding of the Android system kept coming up with answers that simply wouldn't work then got pissed off because I didn't want to choose his answer and flag the question solved.
I think a lot more actual "learning" goes on in this forum per post than the stack overflow model.