PC World posted an analysis on Google's Windows ban

Google's move to ban Windows for internal use was ostensibly for security reasons. But that looks more like a convenient excuse than anything else, because there are plenty of reasons the ban doesn't make sense.

Google's ban of Windows implies that the China attack was a garden-variety Trojan or piece of malware that infected individual PCs. In fact, nothing could be further from the truth. The attack on Google was extremely sophisticated and highly targeted. Dmitri Alperovitch, vice president of threat research for McAfee, told Wired Magazine, "We have never ever, outside of the defense industry, seen commercial industrial companies come under that level of sophisticated attack. It's totally changing the threat model.

  Why Google's Windows Ban Doesn't Make Sense