Blizzard Entertainment, Inc. v Valve Corporation
Blizzard Entertainment, Inc. is the creator of the title Warcraft III, which is the platform the original Defense of the Ancients is created on. By this Opposition, Blizzard seeks to prevent registration by its competitor Valve Corporation ("Valve") of a trademark, DOTA. Claiming that for more than seven years has been used exclusively by Blizzard and its fan community, under license from Blizzard.
IceFrog, widely considered as the most significant contributor to the said game Defense of the Ancients, is currently employed by Valve Corporation in their project of the new title Dota 2.
In the case of Blizzard winning the case, Valve would not be able to trademark the term "DOTA" and this would allow the creation of a new Blizzard title "Blizzard DOTA". Whether Valve would be allowed to continue using their current trademark "Dota 2" is still yet unknown.