I find it somewhat sad to see so many people bag on StackOverflow as if it were a total failure. It's true that there were some negatives, but the brusque attitude and rapid question closures were often in response to a genuine flood of junky, repetitive questions. In its time it was unparalleled and even today there's still useful content on there. I also think its rep system is something a lot of sites could learn from in terms of how to gradually increase user privileges.