There is a tendency in the business world not to hire overqualified job applicants and this very old 1924 article "Why I never hire brilliant men" summarizes the gist of it.
Of course, part of it is that businesses don't want someone to disrupt the cog-and-wheel atmosphere of the workplace, but there is some truth to the article. People don't really talk about the downsides of being "too smart." When you know too much, you can either be overly ambitious and try to do too much (thus being a bad finisher as the article states) or you can be overly depressed and do nothing because you project far into the future. Of course, I think these things can be overcome, but it takes some work. The more brain power you have, the more you have to use to control it.