I don't tend to use StackOverflow all that much. Once in a while I'll look up a poorly documented error code on Google and one of the results will be S.O. But, then again, I tend to stick with languages and libraries with adequate documentation.

Honestly, if one is constantly looking everything up on StackOverflow, they're either using a very poorly documented technology or they might want to hit the books a bit and work on proficiency. "Knowing the literature" is becoming more and more underrated.