I disagree, a virus for Mac OS X would be extremely profitable. Yes, the percentage of Mac OS X users is minimal, when compared to the windows OS user base, but due to the fact that mac users are so confident in the fact that they are virus free, they don't have an antivirus on their computer! This is a virus maker's dream, the OS might have a small user base, but it is UNPROTECTED. But it begs the questioning, why hasn't anyone accomplished this, surely someone, somewhere should have set his sights on not only attacking Mac OS X, but also prettifying all of the Mac OS X users who claim "we don't get viruses" in the process? The answer is simple, the OS is just more secure.
If I were to make viruses, and I saw one of those dumb mac vs. pc commercials where the mac guy would say "buy me and you won't get viruses anymore, because we are immune to viruses", what is the first thing I, as a hacker, would do? I'd get up from my couch and make me a very nice mac virus, just to shut apple up! But have there been viruses since the airing of those annoying commercials, no. The closest things we've had are these spam-ware pests which need us to (stupidly) give them authorization to install!
The argument that Mac don't get viruses because of their small user base is just plain false. And that Alaska air conditioner analogy not only sucked, it was irrelevant, there is a market for hacking Macs, just as there is a market for making mac applications. Think about it. Why are there mac only applications when they can just make a windows application with a much larger user base? Because in marketing you learn that sometimes having a smaller demographic can get you more profit, and a bigger demographic doesn't necessarily get you more sales.