I only read Talent is Overrated, which cited a few studies to the effect that IQ was a bad predictor of professional performance beyond the short term; to become a world-class performer at some specific skill, you need to spend 20000 hours of your life deliberately practicing it (trying things outside your comfort zone, failing to get it right, figuring out what to improve and how, getting it right, trying something harder, rinse and repeat, and it's a pain in the neck). Most people, no matter how smart, tend to stop improving at their jobs after around one year and a half of practice: this includes highly skilled professionals like doctors and lawyers.

And, on the anecdotal side, in my own experience and what I could get from the people that frequent Lesswrong and TVTropes, a high IQ commonly results in huge childhood issues, a miserable social life, and a boatpload of akrasia, which seriously hamper whatever base utility it might have. Perhaps there's a selection bias and only the incompetent brains have the time to hang out here, while competent smart people are too busy actually getting things done?