That's Joel's version of link bait headline. It works nothing like a wiki. But of course, you already know that if you've used Stack Overflow. But, tomato, tomato.
a website that allows collaborative editing of its content and structure by its users.
StackOverflow is a website that allows users to edit the content of questions, answers, and tags. It also allows users to write new questions, new answers, and close existing questions and answers. How is that "nothing like a wiki"?