This slashdot story does indicate an overly broad sense of security in the Mac community, but it's not time to panic.

"The IT security manager of the University of Otago, New Zealand, has been educating his OS X users in security best-practices. According to Mark Borrie, many Mac users believe they were immune to security problems -- a trap many Mac fans seem to have fallen into. He said around 40 percent of the computers at the uni are Macs. "On the security side of things I reckon the Mac community has yet to wake up to security. They think they are immune and typically have this idea that they can do whatever they want on their Macintosh and run what they like," said Borrie. "If I can get our Mac users up to speed and say 'you are not immune' -- so when [the malware] hits, hopefully we will be pretty safe," he said. "We want to be ready for the first big Macintosh virus -- because it will come. Some day, somebody will say 'I am going to create a headline and write a virus for Mac'," said Borrie."

Well, say someone wrote a Mac virus. It's going to try and spread like Windows viruses do. Now, when a Windows virus hits, and tries to infect another system, the odds of hitting a Windows system are pretty good (simply given the large market penetration). Look at Macs, by comparison. Say my Mac gets infected, and immediately tries to infect the other machines on my LAN.

Oops - three Windows boxes, two ReplayTVs, and a Linux box. It's going to find similarly slim pickings (probably slimmer) as it looks outside my LAN. It's not that any given Mac couldn't get infected by malware - it could. It's that the liklihood of an outbreak are very slim.