I forgot how much I like Ars Technica. They have great coverage of Apple technology, the kind I used to get in my MacWeek fix when I was a kid (back when I could tell you the specs of every NuBus or PowerPC Mac being made). Here,. Ars points to Norton places big bet on Mac virtualization vulnerabilities- basically now that you're running OSX and a virtualized WinXP or Vista, you'll need anti virus protection for both.
I think this is a smart move considering that for those of us mac users who have Windows as a secondary OS, updates and patches might not be downloaded in a timely manner, and if you only run the OS for a couple minutes at time,
you're not going to want to spend it downloading updates. So maybe my usual diligence with antivirus software (such as on my office machine) might not be the protection I think it is in a virtualized install.
A strategy to watch.