Walker Digital, owner of travel site Priceline.com, has filed a lawsuit against Activision Blizzard and Zynga for alleged infringement of its patent.
US Patent Number 6,425,828 concerns a "database driven online distributed tournament system," a version of which Walker Digital claims has been used by 24 Blizzard and Zynga products - including World of Warcraft, Mafia Wars and Call of Duty.
The 2002 patent appears to cover a very broad definition of online gaming tournaments, including entry fees, player advancement and prizes.
Walker Digital has not revealed just how much of a damages payment it seeks, claiming it "cannot presently be quantified but will be ascertained through discovery or at trial."
Walker Digital has something of a history of patent suits - it's currently pursuing another against Facebook, concerning the sharing of user information.