Engaging in zero sum competitions with other smart people .
There are whole industries – semiconductors, computers, most software, mobile phones – with too many smart people and not enough dumb ones. (Although, we should note that RIM tried to get less smart by having two presidents, and HP has done their part at least twice.)
This part about the zero-sum competitions is pure genius. Link to the Semel post is here: http://www.quora.com/What-are-some-stupid-things-that-smart-people-do/answer/Lee-Semel-10289