. Some make unusual bedfellows. Supporting Microsoft are Apple, Google and the Electronic Frontier Foundation.

Supporting i4i is a longer list, including 3M, Bayer, 19 venture capital firms, the U.S. government and six former commissioners or directors of the patent office.

"If you look at the group that filed amicus briefs, you can see pretty clearly the companies that filed on Microsoft's side tend to be companies who get a lot of lawsuits against them on patents, and in particular a lot of lawsuits against them by what we call nonpracticing entities," Columbia said. Often called "patent trolls," these companies buy up patents and then seek infringers they can pursue for royalties.