Admittedly, I've not been following the fall out over Google ditching Microsoft with much interest so it's a certainty that I've missed much commentary on the topic. That said: I'm surprised that in the main stream coverage that I have seen, there was no mention of what I believe to be the most important consequence of Big Search's decision.
Some contend that MS Windows is no less secure than any other operating system. While I do not agree with this sentiment, I understand the rationale that with popularity and wide adoption any system can become a more attractive target than others in the same space. As such MS Windows with it's domination of the corporate and home desktop market offers a potentially worthy return on investment for an attacker looking for system to compromise. By this reasoning, Google being a very large enterprise has just painted a huge target on the back of Linux and Mac OS X (users) by making it public knowledge that they will offer only those two options, for desktop computing, to employees. Now attackers know that they have at least one very large and attractive target with millions (yes millions) of computing devices running one of two (not too dissimilar) operating systems that would otherwise not be worth investing the time in compromising.
Just a thought