My comp got a virus that crashed it a few years back, but managed to restore it from the ground up. My mother's laptop crashed a day later. I got really good at system restoration really fast. Bleh.
I think it's more that folks don't write mac viruses nearly as often as they write them for Windows. Mac OS isn't popular enough for trolling, I guess. Though, I do a few friends who have had viruses and crashes on their Macs.