This morning's Apple Insider has an article about how the Flashback Trojan Virus infected 600K Macs last year:
Mac Viruses have been rare compared to PCs, making them a target of opportunity it seems.
What became of Flashback and what did it end up doing?
The detection and removal process looks difficult and it is unclear, to me at least, whether regular Apple software updates will prevent it or hunt it down and remove it.
You can't tell me 600K Mac users need to go into Terminal and diagnose what's going on when most are lucky to know how to do the most basic computer tasks (by design).
Even if you have the Flashback Virus, what is the net downside, did people get ripped off?