Facebook is countersuing Yahoo! with 10 patents of their own. Two of the 10 patents originate from the company. One was acquired on March 30, 2012, two were acquired on February 1, 2010, and another two were acquired December 8, 2011. The other three patents are still being recorded at the U.S. Patent and Trademark Office as being owned by New York University.
When a patent is acquired, the assignment of one entity to another is recorded by the Patent and Trademark Office within three months, but the March 30th patent was recorded the same day as the transfer. Facebook is claiming that Yahoo! is infringing on 10 of their patents, which is the exact number that Yahoo! is asserting against them.