There has never been a successful virus written for Mac OS X, and there is almost no spyware that targets the Mac. Plus, the Mac is invulnerable to viruses and spyware written for Windows. Not only is it more secure, but the Mac operating system is more capable, more modern and more attractive than Windows XP, and just as stable.
Mac OS X = apple's latest windowing system on FreeBSD4.5. I just don't buy it that it is not vulnerable to the same viruses that FreeBSD 4.5 is. I just cannot see how it isn't. Who wrote the article? Do they realize that viruses that can affect OS X may only be listed as FreeBSD viruses?
Myself, I prefer the unadulterated FreeBSD. (Though using QNX now...)
NOTE: all web-browsers are vulnerable to spyware, regardless of the platform, the user is the key.
I'd bet that viruses just don't show up on mac systems in general because the users are generally more knowledgeable. Windows systems are vulnerable because the user does not usually have the first clue.
Anyway, where's that dead horse smiley...?