I really hate slashdot, but I read it anyway. Looking through some comments today, I came across a <A href=http://developers.slashdot.org/comments.pl?sid=56649&cid=5482638>pretty good quote to cut n' paste:
"Diversity, redundacy. These are the basis of true reliability. Sure, Microsoft (for example) can try to secure the shit out of their next OS, but if everybody uses that one product, one mistake takes everyone out."