They certainly exist, but nobody has successfully created one that has spread to the levels seen on Windows system. That's really what I'm referring to: Something that would cause panic in the media, so to speak. Code that attacks a small handful of systems isn't particularly interesting to anyone, no matter what platform it targets, Windows included.

I respectfully disagree. Fully functioning and frequently self-replicating malware does now exist in the wild for the Mac platform.

I've seen drive-by website infections, malicious software installs using social attacks, and malicious attachments infecting Office. When Flashback alone infecting the better part of one million Macs, it is now newsworthy.