If you want it to stay that way, you should probably tell less people to buy a Mac. The only reason mac viruses aren't as widespread is because they have such a small share of the home computer market. As that grows, the OS becomes a bigger and bigger target.
Trust me, I could write a virus for your mac that would make you cry.
i'm sure many people have said that before, considering there are countless scripters out there skilled in that way.
and if that really was that easy, i'm pretty sure it would be widespread by now.