Over 10 million people. Duh!
Currently Word of Warcraft comprises over 12 million active accounts. This number is expected to rise as Cataclysm lures in new players as well as make older players return to the game.
It has 11.5 million monthly subscribers and holds 62% of the massively multiplayer online game market!
Over 4,000,000 and more still making accounts every second!
Last i heard, World of Warcraft had something like 11 million subscribers world wide.