On its first day of release, The Dark Knight DVD sold nearly 3 million copies -- and may top the 7 million mark in its first week of release. That's not quite in the league of a Harry Potter novel -- the last installment of that series, Harry Potter and the Deathly Hallow, sold 11 million copies in its first 24 hours. But you know how today's kids love pages and pages and pages of printed text. If you have to make do with huge cinematic explosions and thrilling urban car/pod chase scenes, like The Dark Knight did, three million copies isn't bad.