Blizzard are appealing against Valve's use of the DOTA trademark. Kotaku have spotted a NeoGaf post that brings to light the appeal notice put before the US Patent and Trademarks office late last year
Blizzard argue that "by attempting to register the mark DOTA, Valve seeks to appropriate the more than seven years of goodwill that Blizzard has developed in the mark DOTA and in its Warcraft III computer game"
The appeal says that the original DOTA mod was originally "distributed, marketed, and promoted by Blizzard and its fans" and is "built upon the 1 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 Battle.net."
Blizzard are busy developing their own version of DOTA , which aims to make a few changes to the formula. They say that the DOTA name "has come to signify the product of years of time and energy expended by Blizzard and by fans of Warcraft III," adding that "Valve has no right to the registration it seeks."
The MOBA genre is becoming a crowded party. There's competition from League of Legends and Heroes of Newerth, and Valve's Dota2 is currently in beta. The question of who owns the genre is a hard one to place, but battles for trademarks are a different matter. Hopefully sparring lawyers won't derail development on either title. According to the trial schedule on NeoGaf, the battle could run until February 2013.