My skin seems to be a very sensitive type that doesn't take well to foreign objects residing within. I've always had problems with piercings, coupled with my line of work which often involves getting dusty/dirty. This doesn't help the sanitation factor and only increases the odds of a rejection.
My nostril ring had been in for a few months straight and I took it out just to sleep one night. The next morning the hole had already partially sealed. I tried my damn best to get it back through, and amidst much blood, cussing, and pain, I eventually gave up.
I do like tongue rings on some people...They are said to help with fallatio...