I think plenty of people tend to vastly overestimate Google's (or Facebook's, ...) hiring bar. I know quite a few people who would be happy to work there and (I believe) can easily beat the hiring process, but they self-eliminate themselves from the game, so I definitely recommend to folks not to make a prejudice about whether they can get into, because they generally don't have many data points, and go interview anyway. Let them figure out whether you are smart enough or not; don't self-eliminate. Never let the widespread propaganda lead you to believe that everyone hired by a successful company in the valley is a genius. They collectively hire many thousands of people; it's hard to believe they are all geniuses.