Is Gadi Evron right that "It's Mac season. The next two years will be interesting"?
Saw this from Darren Herman's Ramblings page. As a Mac user, I can't tell you how many false or useless codecs I've probably downloaded since I started using MacOS X in 2002, just to TRY to play the same media as Windows users could. There is still no way to play Intel Indeo video on a Mac running OSX - not that OS9 is an option.
Mac users like me live in a world where things are improving (the Flip4Mac extensions for Quicktime which extend Quicktime player have been great), it can be frustrating. Plus, if the vulnerability requires you to type the administrator password...well you have to do that pretty much when installing anything.
So, the risk is probably real, but it won't be Klez or Blaster or anything like that, in its current form. The day we get ActiveX on my Mac, I'll worry then.