Unless you follow Mac news pretty closely, you probably missed the recent controversy where Apple posted a knowledge base article suggesting that all Mac users should be running multiple virus detection software packages on their Macs! Apple has since pulled the article saying it was an old article accidentally reposted. CNET has a good post regarding the whole controversy.
My personal feeling is that although the risk is very low (100,000 + viruses for windows and NO know viruses "in the wild" for the Mac), Mac users should still be aware of potential future risks.
The primary risk on a Mac comes from social engineering and phishing scams. These are the ones that are simply tricking YOU into GIVING the bad guys your information.
So the answer to the question, "got a mac virus?" is almost certainly a resounding no! However, you still need to be very aware of scam emails and web sites that are attempting to trick you into simply giving them your information. Makes sense, why write complicated software viruses when you can just get the user to hand over their information.
However, I decided, since I already had some virus protection software for the Mac, I would run a scan on my machine (which I had not done in more than a year) just to see what showed up.
The software I user is made by Intego. I own some of their products because they sell a "Dual Protection" package that lets me keep my Windows OS protected running under Parallels on my Mac. Be aware that running Windows on a Mac does NOT protect the Windows side from all the virus and spyware threats.
So long story short, Virus Barrier scanned my machine and after looking at just under 800,000 files, it found only 3 infected ones. All three were Microsoft Word documents that were email attachments from Windows users I work with. The files had no ill effects on the Mac, but if I had been running the software virus software daily, I would have been able to email the Windows user and let them know they had a problem.
In my opinion, the lesson for Mac users is, be diligent about the social engineering and phishing scams (eg...don't click on links in email from banks requesting your social security number and other similar scams) and if you run virus protection software on your Mac, it will mostly be as a service to your Windows friends to let them know when they are sending out infected files.