We are all notoriously snobbish when it comes to not installing anti-virus software, but largely because we all know that malware is essentially non-existent when it comes to the Mac. Yes, yes, there's the occasional scare, but seriously: when was the last time that you noticed an actual piece of malware on the Mac of someone you know that actually did any harm? Yeah, exactly.
Apple encourages the widespread use of multiple anti-virus utilities so that virus programmers have more than one application to circumvent, thus making the whole virus writing process more difficult.
Of course, Apple has long-touted the fact that Macs just, simply don't get viruses. Remember this ad?
While it's probably a good idea to install anti-virus software, I find it particularly telling that in a self-reported ZDNet survey, 60 percent of respondents don't have anti-virus software on their Mac and don't intend to install any.
I'm definitely in that group.