Yahoo says Facebook data centers may infringe on its patents An employee walks past servers in one of four server rooms at the new Facebook Data Center in Forest City, N.C. (Rainier Ehrhardt / Getty Images / May 3, 2012) Yahoo has warned Facebook that the social networking giant may be infringing on 16 more of its patents. Yahoo sent a letter to Facebook last month alleging that the patents "may be relevant" to technology Facebook uses in its servers and data centers, Facebook disclosed in a regulatory filing Thursday. Facebook has data centers in Oregon and North Carolina. It developed its own servers to power those data centers. Facebook said Yahoo had not threatened a lawsuit but had said "it may do so in the future." The move could be a precursor to declaring a patent war on companies that use open-source software to power data centers. "Yahoo's letter takes aim not just at Facebook but at open-source and energy-efficient green technologies developed and employed by countless innovative, forward-thinking companies and engineers," Facebook said in an emailed statement. We're defending vigorously against Yahoo's current lawsuit, and would likewise do so against any new assertions. A Yahoo spokesman could not be reached for comment. Yahoo sued Facebook in March, alleging that the company was infringing on 10 of its patents. Facebook countersued, asserting that Yahoo was infringing on 10 of its patents. Yahoo then countered that Facebook was trampling on two additional Yahoo patents. Yahoo hired Scott Thompson as its chief executive in January to turn around the beleaguered Internet company. Facebook has bought hundreds of patents from IBM and from AOL (via Microsoft) to defend itself against a rising tide of patent infringement lawsuits. The IBM patents were related to data center operations.