http://www.engadget.com/2010/03/19/charlie-miller-to-reveal-20-zero-day-security-holes-in-mac-os-x/
I like his analogy.
"Mac OS X is like living in a farmhouse in the country with no locks, and Windows is living in a house with bars on the windows in the bad part of town." In other words, Apple users are "safer" (due to the lack of work that goes into hacking them), "but less secure."