<p>The reason that there are comparatively fewer Mac viruses is that there simply aren’t as many Macs as there are PC’s. As a result, hackers get more bang for their buck for targetting PC’s. As Macs increase in market share, they will be targeted more often.</p>
<p>And a relevant article:</p>
<p>[Macs</a> no longer immune to viruses - Security- msnbc.com](<a href=“http://www.msnbc.msn.com/id/12537279/]Macs”>http://www.msnbc.msn.com/id/12537279/)</p>