From the horse’s mouth, Nintendo proper:
Due to delays in the completion of Super Smash Bros. Brawl, we’ve had to change the release date of the game to Sunday, March 9th. I deeply apologize to the people who have looked forward to playing the game for so long and ask that you hold on just a little longer. Thank you for your patience.
Too bad, fortunately there’s No More Heroes, de Blob, and a handful of other unique titles to tide us over. Prediction: Mario Kart Wii gets pushed to summer.