its a thing of effort vs. reward. if i am a hacker, i would try to hit as many people in their respective faces as possible. so yeah, i could try to fuck with these 5-6% which do not use windows, or with the rest. also chances are that mac users are more advanced in technical things, so they arent as easy to trick. then again, it might be tougher to program a mac-virus, so in the end, most people will program a windows-virus.