Actually, it's the other way around. To avoid malware/spyware/virus risks, a lot of people are using a seperate machine for the internet to their main productivity box.

So I'm running UNIX and Mac OS systems that I'm happy to allow online, but as for my work machines and my gaming system, they sit on an isolated network.

I have to say that since I adopted this philosophy, I've had fewer issues with maliscious software, and a far higher level of general stability and control.