Well, I don't know about others, but I do get a few spams a day (3-5 messages), but 95% are caught by Mail's spam scanner and relegated to the junk mail box. It's pretty easy to deal with and administer, day-to-day, and I've never lost anything important.
iMac 21.5", OS X Snow Leopard
2G iPod Touch 16 GB
Strangely enough, I on't get any Spam on my Mac either and that is with the Spam filter at the ISP end turned off (They used to pick up emails in French, German and Italian as Spam, so I had them turn the filter off) and the Spam filter in Apple mail still in the learning mode.
I have had my email address for about 15 years now and use it quite extensively.
I can't really explain why I get no Spam, not that I'm complaining, but when other people complain about getting hundreds of Spam messages daily - I some times wonder.
However, as others mentioned, it shouldn't have anything to do with the Mac or OS X.