When news broke of Apple advising Mac owners to go out an buy an anti-virus solution I personally shrugged it off, I'd seen this kind of advice from Apple before and viewed as nothing more than a command sent down from the legal department. Similar to Apple offering and advising you to use AppleCare hardware.
The problem is, as with many of these types of stories. Those who decided to write it up have done so without proper research and have caused a cascade of misinformation; to the point where the BBC is writing up the "news" which quickly became one of the most viewed stories on the site and remains as of writing the most emailed.
Thankfully one blogger has done the hard work that everyone else should have done and pointed out that the support technote that Apple posted on November 21 (updated December 2) was in fact an amended article which was originally posted on Apple's site in June 2007.
So Apple has been offering this recommendation for 18 or so months although even Apple claims that the article "does not constitute Apple’s recommendation or endorsement" but is only their for "information purposes".
And before everyone jumps on my back I do see the importance of running anti-virus software in networked environments where Windows PCs are present and maybe even as just a precaution on your Mac, but you won't catch me running one of these bloated third-party anti-virus applications.