If inauthentic copies of open source software became an issue it would inevitably lead to wider, more-friendly, adoption of MD5 checksumming -- perhaps directly into software update utilities. This should be happening anyway, even without an eminent threat.
I'm not sure how MS has the upper-hand here. Speaking theoretically, the Linux community would respond by saying, "You've obtained an inauthentic copy, here is how you can freely fix it." The MS response is, "You thief. How dare you run a piece of overpriced software without obtaining proper licensing. You will bow to our capitalist ways, or else suffer with malware." As a person in X country, living with only Y amount of income, decide which side you are going to take.
For that reason, I welcome MS to do these things. They need to truly come out and show the beast that they are so people will finally wake up. With the Mac-mini at such an attractive price and Linux slowly maturing, people have less reason to remain in the Microsoft Kingdom.