There is a serious concern in that. Spy agencies buy and commission zero-day exploits. Compared to the cost of satellites, they can easily spend so lavishly that exploit authors have an incentive to worm their way into open source projects. That quite a bit less direct than buying or commanding a back door in a proprietary product, but it's going to be difficult to defend against. It will be interesting to see if such shenanigans are ever uncovered due to the "many eyes" approach.

We get to see a an interesting experiment, that was previously only a thought-experiment. The classic "market share" argument gets put to the test: "Windows only attracts malware because Windows runs on the most computers."

If Microsoft and Windows stalwarts believe in that strongly enough, they should be in favor of seeing PRC adopt Linux.

AV/firewall software already exists for linux. I don't really see how it would change muc, aside from popularity.

I asume the majority of people currently using Ubuntu are smart enough to avoid malware.

Switch to OpenBSD.