I've said it before: SO is useful for the first 5 years of a software engineer's life. After that, it's occasionally useful when you need to pick up a new technology. The questions that are hard, for real senior software engineers, are rarely found on SE sites. Programmers.SE was supposed to fix it, but it hasn't worked, because of the same moderation.
This is a moderation problem, but the solution chosen was the easy solution: just don't allow hard questions because hard questions beget arguments. Instead, requiring people to have civil discourse, perhaps even requiring that people show they can have civil discourse before allowing them to participate, is much, much more difficult.
I'm not sure SE could survive the second type of moderation. But by not having it, it certainly makes it usefulness to somebody like me, with many years of experience learning and using various technologies, near zero.
1. http://programmers.stackexchange.com/questions/181342/r-vs-p... [closed as off topic]