Blizzard Fights with Valve Over DOTA Trademark

Blizzard's DOTA legal filing with the United States Patent and Trademark Office (USPTO) was submitted on November 16, 2011
As you may remember, back in August 2010, Valve filed a copyright claim on the term DOTA. After two months, in October 2010, Valve announced DOTA 2, a game in the works at IceFrog and based on the very popular Warcraft III mod, Defense Of The Ancients. Now, NeoGAF is reporting that Blizzard Entertainment filed a complaint against Valve's registration over the DOTA 2 name. "By this Opposition, Blizzard seeks to prevent registration by its competitor Valve Corporation ("Valve") of a trademark, DOTA, that for more than seven years has been used exclusively by Blizzard and its fan community, under license from Blizzard. By virtue of that use, the DOTA mark has become firmly associated in the mind of consumers with Blizzard, including to signify a highly popular scenario or variant of one of Blizzard's best-selling computer games, Warcraft III. Over the past seven years, the mark DOTA has been used exclusively in connection with Blizzard and its products, namely Warcraft III. Most notably, DOTA has been used as the popular name of a Warcraft III software "mod" file that has been distributed, marketed, and promoted by Blizzard and its fans (under license from Blizzard); that utilizes and is built upon the Warcraft III game engine, interface, and gameplay mechanics; that is comprised of Warcraft III characters, items, spells, artwork, textures, and color palates; that can be played only using Warcraft III software and via Blizzard's online service ; and whose name (DOTA, an acronym for "Defense of the Ancients") is a reference to Warcraft III characters known as the "Ancients." More details here.