Classic bait and switch. That's how things have played out since Geocities. You young guns sweating over Stack Exchange points don't remember those days. That's why you register a dot-com, to protect your content.
It's just another content farm looking for unpaid labor.
Because it's an excellent resource, it could be monetized with a paywall. We can't predict the future but we can learn from the past.
They're already monetizing it with http://careers.stackoverflow.com/employer
They don't really have much competition but I think http://snipt.net/ is a good alternative in certain situations.