No No No No No...
This is utter crap peddled by the fanboys.
Unix can get infected.
Linux can get Infected
Mac's can get infected.
Try searching for Adobe Mac Exploit for an example.
Yes it's required less, but it is still required. But as Mac's become more popular, watch the number of attacks become more prevelant.
Also note that Apple are very slow to patch, so any falw found in the wild may be around for some time.
Robert Wilensky:
We've all heard that a million monkeys banging on a million typewriters will eventually reproduce the entire works of Shakespeare. Now, thanks to the Internet, we know this is not true.