Online real-time strategy game League of Legends, from Riot Games, is the latest large web property - Wikipedia credits the game with over 32 million registrations and millions of active players every day - to own up to a data breach. The game is divided into three regions (earthly regions, that is, not regions inside the game itself): North America, EU West and EU Nordic and East.
Riot Games has published its security warning only on the European side of the Atlantic, suggesting that North American players are off the hook:
More at Sophos blog: League of Legends online game joins the League of the Hacked | Naked Security