I'd love to run without anti-virus and anti-spyware, but children (especially teenagers) are incredibly adept at filling any PC with trojans and viruses in a matter of minutes. They even know how to bypass most internet filter software. I sometimes think children are viruses!
Seen on a comment on a Coding Horror post about the performance hit of antivirus software (what we really need is Anti-Anti-Virus software to keep us safe from the ongoing Anti-Virus software pandemic).
Ory Segal (an IBMer after watchfire's acquisition) also "celebrates" 20 years of anti-virus software.