In our various meetups and briefings with Google employees in the Seattle region, it was once common to see them using Windows PCs, frequently IBM (and later Lenovo) ThinkPad notebooks. But more recently, it has become more common to see a Googler pull out a MacBook Pro.

And it turns out that there is, in fact, a reason.

Confirming rumors we've been hearing for a while, the Financial Times reported yesterday that Google has decided to phase out Microsoft Windows and shift to Mac OS X and Linux on employee computers. The story says the policy was motivated by the high-profile hacking of Google's network in China.

Which means, of course, that we've got a good old-fashioned Windows vs. Mac vs. Linux security debate on our hands as we return from the long holiday weekend. There's a competitive subplot in all of this, as well, with Google preparing to release its Linux-based Chrome OS.

"Windows is known for being more vulnerable to attacks by hackers and more susceptible to computer viruses than other operating systems," the Financial Times wrote. "The greater number of attacks on Windows has much to do with its prevalence, which has made it a bigger target for attackers."

Microsoft's communications chief, Frank Shaw, responded to the Financial Times story in a series of tweets, raising questions about Google's motivations for the shift and suggesting that it would be disingenuous for the search company to cite Windows security issues as the reason for the change.

Writes Ryan Naraine of ZDNet: "This story makes little sense to me. For starters, Google’s software products are made for — and marketed to — mainly Windows users. How exactly are software developers expected to build products for an operating system when they’re not allowed to use it? As much as we love to bash on Microsoft over security, the newest versions of the Windows operating system are by far the most difficult to penetrate."

A vulnerability in Microsoft's Internet Explorer was, in fact, acknowledged to be one of the means by which Google was hacked, along with social engineering tactics. At the same time, the exploit reportedly took advantage of Internet Explorer 6 running on Windows XP, not the latest versions of the Microsoft browser and operating system.

For what it's worth, this has been in the works for a while. I first heard the rumor about Google shifting to Macs several weeks ago, along the lines of what the Financial Times has now reported, but despite digging into it for an afternoon, I wasn't able to nail it down, and unfortunately it never made it off my list of tips in need of further investigation. (I'm now kicking myself, for the record.)

When I contacted Google back then, a spokesman responded, "We're always working to improve the efficiency of our business, but we're not going to comment on specific operational matters." The spokesman reiterated that statement today.

Update Wednesday morning: Here's Microsoft's response on the matter, defending the security of Windows in this blog post.