VGChartz claims StarCraft II is on track to become one of the fastest selling PC games of all time. Around 1.8 million copies have been sold across the Americas and Europe, and this doesn't even include sales from StarCraft-crazy Korea:
Early data is in and it looks like StarCraft II: Wings of Liberty has become the fastest-selling game of 2010 to date and one of the fastest-selling PC games of all time. VGChartz estimates that around 1.8 million units of the game were sold on day 1 across the Americas and Europe including both physical retail sales and Battle.net download sales. This figure does not include players in Korea where it is virtually impossible to accurately estimate how many people will have purchased the game due to the way in which it is sold - mainly via time cards and also with Blizzard announcing that World of Warcraft users with an active account in Korea would be able to play the game free of charge. The number of players in Korea playing the game on day 1 could be as high at 3-4 million but only Blizzard will know for sure.