Blizzard made the following announcement regarding sales figures today for WoW over the Holiday season:

World of Warcraft Dominates Holiday Sales
This holiday season, demand for World of Warcraft was so great that more than 600,000 copies of the game were purchased by customers in North America, Australia, and New Zealand. With so many copies of World of Warcraft installed, the game went on to shatter all previous concurrency records in North America, achieving over 200,000 simultaneous players during the holiday period. Please see the full press release for more details on these momentous achievements.