I've got Firefox and Safari on our Mac, but viruses don't seem to be an issue with these things.
After reading your original posting about StupidpC I did a quick search to see what sort of viruses have been found for the Mac, virtually none for the OSX, there seems to be a debate as to why. Some feel it has to do with the user base being more computer savy/programmers that would be able to make counter measures at will, the fact that the Mac has less than 10% of the market so where is the fun in annoying only 10% and still others believe it is due to the open source/ better, more secure O/S or any combination of the above.
I personally favor the notion viruses are made just to prove a point to MS out of sheer hatered towards them. And then Apple goes spouting off about how there are no virus problems for them and poof a few pop up just like that back in 2006