"Windows 7 is actually more secure than OS X, but the gap narrows every year. And there simply isn’t the same attack ecosystem for Macs, nor are we likely to see one develop.
So while Mac users will likely see more malware, it’s highly improbable we (or Windows 7 users) will ever experience what those who are still running Windows XP battle today.
But two other factors are changing the Mac security landscape. First, Apple products are growing rapidly in popularity. At the same time, the overall Internet security environment is more hostile than a cantina on Tatooine."