Google may turn over information about third-party keyword purchases after being subpoenaed by a recreational flooring company.

Santa Clara University law professor and tech law blogger Eric Goldman alerted readers to the subpoena in a recent blog post last week, warning that this sort of legal action could give businesses access to private information about the advertising habits of competitors.

"Were this to become commonplace, it could completely change the current equilibrium with respect to Google's AdWords program," Goldman told The Register.

The subpoena is part of an ongoing District Court case between Rhino Sports and Conner Sport Court International, two companies that sell flooring for athletic facilities, including basketball courts, tennis courts, and baseball batting cages. In 2002, Conner - previously known as Sport Court - sued Rhino for trademark infringement, and a year later, Rhino agreed to an injunction restricting it from using the "Sport Court" trademark "on or in connection with the Internet." That includes internet domain names, sponsored links, and any HTML code, "such as the title or keyword portions of a metatag."

Then, in early May of this year, Conner accused Rhino of violating the injunction, claiming that the company had purchased the "sport court" keyword phrase on Google AdWords.

As Eric Goldman pointed out in an earlier post, Rhino had merely purchased the "broad match" terms "court" and "basketball court," not the specific term "sport court." The court rejected Conner's claim, but Conner has now issued a subpoena to Google, requesting information on "all purchases of 'sport court' as a keyword," "associated cost per click calculations," "estimated ad positions for the keyword," and "search volume trends for the keyword." That includes information about Rhino's AdWords account as well as the accounts of other businesses. That's right: Businesses not involved in the case.

Google did not respond to our request for comment, but it seems that the company will comply with the subpoena - if there aren't complaints to the court. Goldman posted a copy of a letter Google sent to all affected businesses, explaining that information related to their AdWords accounts would be turned over to the District Court unless they file an objection to subpoena.