Apple had occasional problems with viruses several years ago when they were selling far fewer computers. Since then, Apple has switched to Mac OS X and is selling Macs in record numbers - and not a single virus has spread in the wild. Your theory is discredited.
I'm not so sure that will continue with Apple's embracing of the Intel processor. Granted, dll-loading and system API calls within the virus code designed for Windows will not work, but I'd still think hackers could now have the capability to write platform-agnostic viruses for Intel that could do a phenomenal amount of damage. Your thoughts?
But there have been as noted above. The new vista requires users to say yes when running as admin as well; however, I bet the excuse antirepublicrat uses won't be acceptable for Microsoft when idiot users click on a link and say yes to allow admin access and wammo virus hits. The fact that most machines will be windows it's more likely that a virus writer will gamble that even if 1% of the users are dumb enough to say yes...they'll catch hundreds of thousands if not millions of users with their virus. If you catch 1% of the mac users that say yes to an admin access request...then you have caught hundreds of people. Not exactly newsworthy.