I remember reading something about that causing low sperm count. The testicles are meant to be kept cool - that's why they are not on the inside of the body but hang outside in a sack.
I believe that a heat source constantly on his crotch is not good for his vitality. I'm not sure if or how this would affect his personality or ability to become erect.
Regardless, he should get a laptop lap pad. My boyfriend has one, and I'm always stealing it when my laptop gets too hot. Get one for both of you! All it does is create a bit of distance between your 'puter and you and gives some ventilation. It's good for the computer too!