That when you are running Windows, you actually are running Windows like any standard PC, and THAT is the main security concern that people have. However, if you install other software to make the Mac partition available to Windows, then anyone who get a hold of your system in Windows could muck with your Mac partition. The Mac OS itself isn't any worse off, it's just that Windows screws up the security bubble a bit.
Well Gartner seems to say so. But wasn't it analyst's that said that Podcasts were a mere blip on the screen?