Sorry, the "not enough out there" argument doesn't fly. There are millions more sold every month.
Since most viruses are written merely to cause mayhem, and not for $$$ gain, why would any virus writer bent on destruction want to attack those smug, cocky, virus free Mac users? sarcasm. Virus writers are like thieves. They go for what's easy.
The hacker who wrote the virus that caused widespread havoc in the Mac world would be a deity to other hackers.
And yes, Macs can be hacked. They are simply a machine. But they are more difficult to hack because of Unix underpinnings. Since the root account is disabled by default and it takes a particular order of steps to enable it, the widespread self-replicating viruses that attack Windows machines have yet to materialize in the wild.
As far as not worth the hassle, if they are out for money the Mac base is where that's at.
The Mac vs PC argument will never end, but this line of reasoning doesn't work anymore.