Ever heard the phrase "I use linux, so I don't have to worry about using a virus scanner. Linux doesn't get viruses!" Famous last words! Viruslist.com has an interesting blog post on the topic.
Viruses: not a Linux problem? : Virus Analyst's Diary - "More and more organizations are starting to use Linux alongside Windows, with a Linux file-server storing Windows applications. These files can be infected at desktop level, with infected files then being stored on the server. Organizations must therefore accept the necessity of scanning the Linux server to protect against malicious code attacks.