I used to hate and usually refused. Then in night class last semseter we ALL had to take turns in front of the camera. If you refused to model, you were not allowed to shoot either. So of course we all goofed around and out of 24 exps one would be lucky if you had got a decent "glamour headshot". Most of them were of sneers, tongues sticking out, over acting/poses, the angry rockstar, or pouting child look. My favourite was the self inflicted rabbit ears.
After seeing the absolute worst portraits one could possibly pose/take, it doesn't bother me so much anymore.