Nope, they do not use hidden divs. They only display the answers if a) you are Googlebot, coming from a Google IP address, or b) when you HTTP referer contains

Nope, they do not use hidden divs. They only display the answers if a) you are Googlebot, coming from a Google IP address, or b) when you HTTP referer contains google.com. If it weren't for the latter, they would be banned by Google. Of course, they still hide the answers all the way on the bottom of a very long page. Kind of related: Ever since the advance of "open" sites like Quora and StackOverflow I have not seen Expertsexchange[0] in my results anymore. 0: I still can't read that name without snickering.