Earlier this year, Blizzard let people pre-order and then download StarCraft II via its Battle.net online service. However, the people who got the downloadable version only were not able to play the RTS game until several hours after the game started being sold in retail stores.

Now Blizzard has announced a similar pre-order and download program for its MMO expansion pack World of WarCraft Cataclysm. During the opening ceremonies at BlizzCon today it was revealed that downloadable pre-orders will begin soon and people who buy the expansion will be able to play when the servers go live at midnight December 7.