never had a provable virus, but...
I ran AV programs and multiple anti-spyware programs (on Windows XP). Never had a virus, but had a piece of spyware indistinguishable from one (pop-up, after pop-up, after pop-up -- I had to reboot to Safe Mode to get rid of it).
No one has the resources to check everything. Any advertising--supported media has a disinclination to negatively review their advertisers.
I once subscribed to 4 Macintosh magazines. The one I believed had on ads (but cost 5-10 times as much).
You get what you pay for (sometimes).