Though normally seen as rivals, Microsoft and Google have joined forces to sue a patent troll, Texas company GeoTag Inc., and have its patent invalidated. Since July last year, GeoTag has sued at least 397 different companies, including Boeing, Pizza Hut, and Rolex, claiming patent infringement. Microsoft and Google are together arguing that the patent should not have been granted, due to the existence of prior art.

The patent, 5930474, covers any system which depicts geographical data, either in the form of a map or text, and then provides information about resources (goods and services) available in that geographical area. Covered systems combine geography/mapping databases, Yellow Pages-style databases, and "local content" databases, that glue the two together by storing which companies (etc.) are available in a given geographical area.

Most or all of the 397 companies being sued by GeoTag Inc. are being sued because their websites include store locator features—put in your ZIP or postal code, see the stores nearby, with the information usually presented on a map. That map is, in turn, often provided by Google Maps or Bing Maps, making these companies Google and Microsoft customers.

The two companies are asserting that their products and their customers' use of those products do not infringe on any of the patent's valid claims, and are seeking a permanent injunction preventing GeoTag Inc. from suing any Microsoft or Google customers. Further, the companies are seeking to have some or all of the claims made in the patent invalidated, claiming that there was prior art that the USPTO should have considered when granting the patent.

The patent itself has had a colorful history. Filed in 1996, granted in 1999, it has been sold and re-sold by various entities residing in some of the world's tax havens including Liechtenstein and the British Virgin Islands. Around two years ago it was sold for $119 million to Antigua-based electronic payment services firm Ubixo Limited (formerly M2 Global Ltd), and in July 2010 Ubixo spun off GeoTag as a separate company. GeoTag is now attempting to raise capital with an IPO. GeoTag's only substantial asset is the patent (even going so far as to proudly boast about it on its homepage), making it a classic patent troll—it didn't create the patent and has no products using the patent; it exists only to sue companies that it believes to be infringing.

Google and Microsoft have found themselves on the same side in patent battles before. In Microsoft's long-running case against XML company i4i, currently being appealed by Microsoft, Google has filed an amicus brief, expressing support for Redmond's position.