And then there's my old manager who found a negative correlation between a programmer's ability and them holding a PhD in CS. FWIW, he had a MS in Software Engineering himself and he said that the correlation only seemed to hold for CS PhD's, not PhD's in other sciences. My department had a number of PhD's, but only one in CS and that one was hired a few years after that manager left.

Correlation isn't causation and all that, but it does bias you a certain way.