Actually, the apple products are less affected by virus/spyware but that only because the market is much more smaller than the PC market.
People say that MAC is much more secure than Windows. I'm not agree with this. MAC also have is flaws, that's only because hacker/virus creator (and the other) aren't interest to it because, as I said, the market is much smaller and they want to hit big, so they target PC.
That said, it doesn't mean you don't need an AntiVirus or any other protection. YOU SHOULD have it, because there a tendency for more virus for mac as the mac market slowly grow.