I wouldn't be bothered about not getting one if I'd never been on the forums and seen people saying 'My good man, I only give a commendation when someone has played truly exceptionally. I do not believe that you are deserving of my commendation just for doing your job. Hurf blurf I've never kissed a girl.'

So now when I don't get one (because tank commends healer, healer commends tank, dps commend each other) I'm always suspicious that I got that self-aggrandizing muppet.

Seriously, they cost nothing to give. Unless the run was a total mess with everyone screaming like idiots I always give it to someone.