Mac, meet virus.

Apple has enjoyed a pleasant lack of any real attention in the virus department for years, mostly due to their insignificant market share (historically less than 8% and thats in the united states where their sales are strongest.) Well, as market share rises, it turns out that the virus resistance Mac always bragged about was mostly accidental. Mac support has officialy changed their stance

"Apple encourages the widespread use of multiple antivirus utilities so that virus programmers have more than one application to circumvent, thus making the whole virus writing process more difficult. Here are some available antivirus utilities:

• Intego VirusBarrier X5, available from the Apple Online Store
  License: commercial
• Symantec Norton Anti-Virus 11 for Macintosh, available from the Apple Online Store
  License: commercial
• McAfee VirusScan for Mac
  License: commercial

In addition, Mac ads claiming that mac didn't need anti-virus have quitly dissapeared from apple, and possibly at their request, youtube. 

http://www.youtube.com/watch?v=RYPWFF9Sty4