"It's easy to get bored with routine and hard to extract gratification from normal conversation, at least with most members of the bar crowd."
An interview with Christopher Langan, who's worked for years as a bar bouncer and has an IQ of 195. (PDF, via Metafilter.)
Are there lots of really intelligent people who are only marginally employed? Or do you think that if they are, they probably have mental problems? Perhaps they're only bored will all the things that everyone else finds interesting, and they are disabled from living in the world as all the ordinary people have arranged it.