Net Applications noticed something unusual with stats from Google.com, which would represent Google (NASDAQ: GOOG) employees, not the public at large that use its search engine. Two-thirds of the visitors from Google.com did not hide what operating system they were running, which Net Applications recorded in its survey.

One-third, however, were unrecognized even though Net Applications' sensors can detect all major operating systems including most flavors of Unix and Linux. Even Microsoft's new Windows 7, which is deployed internally at Microsoft headquarters, would show up by its identifier string. But the Google operating systems were specifically blocked.

"We have never seen an OS stripped off the user agent string before," Vizzaccaro told InternetNews.com. "I believe you have to arrange to have that happen, it's not something we've seen before with a proxy server. All I can tell you is there's a good percentage of the people at Google showing up [at Web pages] with their OS hidden."

So what's Google hiding?