user error causes viruses
It is user error that causes viruses to get on machines. A virus can't get on your machine without you telling it to get on your machine (in one way or another). My Windows LT stays virus free as long as I don't let anyone else use it. On my home Windows desktop I have to keep virus software on because my wife and kids can't stop clicking on stupid stuff. My Windows LT and my Ubuntu LT have had the same number of viruses over the past 2 years: 0.
At the moment, the large majority of Linux users are knowledgeable in cyber security. The more the OS gets mainstream, the more "ID10T" errors will show up because more non-trained folks will start using them. The more mainstream an OS is, the more viruses are written for it. The combination of these two will mean that, yes, there will be more viruses for Linux. As many as for Windows? I doubt it, but viruses will infect those who can't help but click on stuff no matter what OS they run.
