Mac security is not perfect (of course) but we've got to compare to the alternative when making choices.

John Welch writes an interesting and informative article about the state of security on Macs at bynkii.com:
On why the Mac's small population is not a defense against an attack

I agree with most of what John concludes - Macs are NOT invulnerable, obviously. I had to deal with what measures to take for the SSH bug, along with several others. Those were bugs which a savvy, malicious programmer could have exploited to obtain root access remotely.

However, most people would be well-served to play the odds. The consultants that have the skills (and time!) to lock down Windows to the point of being both as secure and yet still USEFUL as most *nix operating systems does not nearly cover the number of places such systems are needed. Therefore, most businesses (and home users) would be well-served to avoid Windows like the plague it usually is.

We'd all be better off. The Windows users would be less likely to have their private information (ID, credit cards, network passwords, etc) stolen, and EVERYONE would have less zombie-spewed spam to deal with.

I think it's important to realize that we're not doing an analysis of Mac security in a vacuum. We've got to compare it with the alternative. When you do that, the choice is blindingly obvious: either spend years becoming a top-flight Windows security guru, or use Macs (and not be abjectly stupid in securing them).