The MPAA is under the assumption that they are responsible for the runaway success of The Dark Knight, based on their recent anti-piracy campaign. Never mind the fact that the movie has been more heavily anticipated than any in recent memory, and that the marketing campaign has been one of the most clever and pervasive that anyone can remember. The MPAA misguidedly credits themselves for the business.
Of course, this is all a paranoid smokescreen that the MPAA is using as a last stand so that they can point to their lawsuits and scream, "SEE! If you outlaw file sharing, we could all make this kind of money all the time!" However, what they fail to take into account is that almost all of the movies on Earth suck, and The Dark Knight is a once-in-a-lifetime event.