This topic was posted at Less Wrong (by Phil Goetz), but apparently Eliezer thought it would fit better here.

Wow - I didn't remember seeing this on LW, even though I have a comment there ("It might have been more on-topic for Overcoming Bias than Less Wrong, but I'm voting up because this is a data point in a topic that's frequently come up in both places"). My apologies to Phil Goetz for not linking to his post!