You may be hearing some nonsense from the diehard PC users, especially the clueless John Dvorak, about the Mac OS being hacked or vulnerable. The bulk of the story comes from the CanSecWest Security Conference in Vancouver. Truth is, they had to change the rules for anyone to succeed and even then it was only through Safari (default web browser for Mac OS X to you Windows users). Still no success taking command of the overall system or the critical root user which would really spell game over. So as long as you’re not visiting questionable sites on the Internet, aka file-swapping or places of unknown origin, I wouldn’t sweat this. You should still always take precautions, stay on top of your finances if you do online banking and change cricital passwords at regular intervals, etc. As my Unix teacher Mr. Kochis taught me, over 80 percent of security breaches with computers are caused by human laziness.
I would like to see proof of a real-world attempt yet nobody has produced one to my knowledge. Well, without the use of third party devices that are known to be flawed such as Chicken of the VNC or the wireless card the security company knew had a problem.