I've been using computers of various kinds since the mid-80s, including Windows from 2.0 up to 8, Atari, Amiga, various Linux distros and most recently Mac OSX. I wouldn't dream of putting a Windows box into production without antivirus software. I've seen serious virus outbreaks on all of the platforms I've used, apart from Linux and OSX. I've never had active (continuous scanning / file protection) antivirus on Linux or OSX and I've never seen a virus infection. In all my years of supporting friends and family and various corporate systems, I've never had to clean off an infected OSX or Linux box. It's just never happened. So maybe I'm deluded or pretentious, but I'll install active antivirus on my Mac once I've seen a single example of a serious infection in the wild. Until then, I'll keep Clam on standby.