In 2003, a company named Medien Patent Verwaltung showed Warner Bros their technology to mark films in a way capable of tracing a pirated copy back to its origin theatre. And allegedly, WB has been using the tech since... without paying.
MPV has a patent on their technology and is suing with that in hand. Interestingly enough, WB has a patent on some sort of "Motion Picture and Anti-Piracy Coding" as well.
While the courts will need to decide whether or not MPV's claim is true, the entertainment value from the accusation itself is enough to justify all the pangs of international patent law. [HollywoodReporter via Escapist via Slashdot]