I work as a unix sysadmin for a federal department. There have been times when in trying to troubleshoot something for a user (e.g. users in another government department who were trying to get theirs to add a firewall rule to allow them to use our online payment site for their transactions) when I have been asked by SECURITY people who my servers are not running anti-virus software.

Because allowing https traffic to our server not running Norton (or insert your favourite) is a huge risk.