"PCs, not Macs"

from here

Many people really did believe quite earnestly that Macs weren't going to have the malware problems PCs did. One otherwise smart individual even went so far as to perform an ill-conceived game-theory analysis to support that idea. The problem was even when that analysis was performed there already was malware for the Mac, and not just proof of concept malware either. There was financially motivated Mac malware that had been ported over from the PC platform. Now, however, we seem to have a sophisticated piece of Mac malware that has no PC counterpart - it's exclusively for the Mac.

Macs may never see the same volume of malware, but they are just as vulnerable to malware as any other platform, and they've been a target for years.