Seeing as i started this thread almost 4 years ago, i'll fill you in on what happened.
I have a form of a rosacea that started showing up around the same time i bought that iMac. It hasn't really gone away, even though I've switched computers twice. It comes and goes, and if i use a moisturizer once a day for a week or two, it usually goes away.
I think it's probably just a coincidence.