Its "rife" because it's targeted. Lets face it, you can't cripple a bank or government by writing a virus for linux. I love Linux and use it as my daily driver, although I do have command line AVG running in the background. I'm careful anyway though. I only use windows as a VM to handle things that Ubuntu (including wine) cannot do so I don't have an AV. When I did, I did pay for it. Simply because at that time, things like Nod32, BitDefender, Kaspersky WERE better than free versions. I always used to keep a close eye on the PcPro Labs tests, until Avira became the 2nd best AV - which was free.