A billion Windows-using PCs? Not even Microsoft is claiming that they’ve sold 1 billion Windows licenses. Let’s stay within the realm of reason.
As for the “hacker’s point of view,” I already addressed that with my rhetorical question about sieging the fortress versus pillaging the defenseless villagers. Why would a hacker go to the trouble of breaking OS X—which is built on UNIX—if the motivation is to profit in some manner? It’s not worth the effort when this same hypothetical hacker can just go write up a quick Windows script and get a zombie network operating within minutes. The alternative motive is fame and infamy, but ask yourself: why is it that after almost a decade, none of these fame-seeking hackers have legitimately exploited OS X? Since the Intel transition 3 years ago, Apple has been a high-visibility target, and yet… nothing. Surely some hypothetical hacker would have exploited OS X by now just to shut up the hypothetical legions of brainwashed Apple fanboys, right?
So let’s be honest here, OS X has not been exploited not for a lack of effort, but because it has no gaping holes in its defense. There are very likely holes, but after 10 years of OS X’s existence and another 30 years of UNIX’s existence, I’m starting to doubt they’ll be found.
I also forgot to add the PC users with illegitimate versions of Windows. Worldwide, there may be more hacked/pirated version of Windows running than total Mac systems. I am not stating this as a fact as I do not know, but in third world countries where piracy is rampant you know there is a huge segment running Windows illegally. Millions upon millions.