The amount of false information going around that is factless and not correct is amazing to me.
First, be it Mac, Windows, or Unix doesn't matter at all. They are all just computers with hardware and an OS. You can exploit anything at anytime, it's just a matter of when. In fact, the first computer virus ever reported in the wild was on an old Unix system a good 30 years ago or so. This was the first time someone had written code that would act in a way to harm someones system and continue to spread.
Second, Macs are just like anything else, you have to secure them properly and know how to use them. Saying Macs still don't get viruses, malware or whatever is totally false. It is just not targeted as much because these people go where the most money is which is the largest platform. At this time that happens to be Windows still. But any IT guy will tell you EVERY OS out there can and does have viruses, come under attack, etc.
Third, this one is just the most wide spread at this time on the Mac and it is changing. I HIGHLY recommend listening to shows like Security Now for more on this and other security news where you can get real facts from real security experts.