"Google's acceding to the request would suggest that it is willing to reveal information about those who use its services," wrote U.S. Google attorney Ashok Ramani in an Oct. 10 letter to U.S. Dept of Justice attorney Joel McElvain. "And one can envision scenarios where queries alone could reveal identifying information about a specific Google user, which is another outcome that Google cannot accept," the letter continued.

Although Ramani didn't spell out how a query could in itself reveal identifying information, commentators have suggested this result could happen when users search for their own names. Ramani also objected to the subpoena on the grounds that compliance would reveal trade secrets and proprietary information.

Last August, the U.S. government subpoenaed records from Google in an effort to prove the 1998 federal Children's Online Protection Act--which forbids commercial Web sites from making pornographic material available to children--is constitutional. As a practical matter, such sites would have had to require registration or credit card verification to make sure that children weren't accessing them. In 2004, the U.S. Supreme Court said the law couldn't be enforced unless the government proved that it was the only practical way to shield minors from adult-oriented sites.

Now, in an effort to prove that adult Web sites remain readily accessible by minors, the Justice Department has subpoenaed search records from Google, as well as MSN, Yahoo!, and America Online. The other companies all complied.

While the subpoenas were served last summer, the matter was kept secret until Thursday, when the story broke in the San Jose Mercury News. By the end of the week, court documents, including McElvain's declaration, surfaced online.

For Google, much is at stake, as the company increasingly tries to convince users to sign up for personalized services such as e-mail, instant messaging, and customized home pages. Although the company hasn't said exactly what it intends to do with users' personal information, many predict that Google and other search companies will use demographic information to target ads more precisely. Independent of the government's recent subpoena, privacy advocates have been increasingly concerned that Google, and other search companies, are amassing massive profiles of users--and that the companies could theoretically connect searches conducted and Web sites visited with users' offline identities.

The specter of that happening grew last week, with the revelation that the government was trying to get information from Google. By the weekend, stories advising users how to protect their privacy appeared in mainstream media like Wired.com, which ran a piece titled "How to Foil Search Engine Snoops" that advised readers to delete their cookies weekly and consider routing searches through Web anonymizers, like the Electronic Frontier Foundation's Tor.

The uproar also led Ken Moss, general manager of MSN Web Search, to issue a blog post Friday emphasizing that MSN hadn't turned over any personal information. "[W]e produced a random sample of pages from our index and some aggregated query logs that listed queries and how often they occurred. Absolutely no personal data was involved," he wrote.

This news story is important. I recommend that everyone read it.