Not only is the rate of production of new malware increasing but gaining in sophistication too:
“in the last month alone two new malware samples were undetected by all 42 virus scanners and many were detected by only a handful of products. “
Malware, alone, is more than enough reason to migrate to GNU/Linux which is a much more resilient OS, harder to penetrate, and not event the target of most malware. I recommend Debian GNU/Linux because it works for you and not M$, its “partners” and definitely not for malware artists.
See Michael Horowitz – How useful is antivirus software? | Computerworld Blogs.