Blizzard and Valve to man the lawyer cannons over two upcoming games, DOTA 2 from Valve and Blizzard DOTA from Blizzard. The companies have reached an agreement, however, which includes Blizzard renaming its game to Blizzard All-Stars while retaining use of the "dota" name for noncommercial use in the fan community. Valve retains the commercial use of the name.
It sounds like a little matter until you remember that Warcraft III was the source of the map that spawned this game type, leading to both companies developing competing versions of a sequel. Blizzard All-Stars currently has no release date, while DOTA 2 is due out sometime next year and is currently in beta testing. Luckily, the terminology is only being changed on the corporate side, meaning players are free to continue discussing the games as they would have anyway.