Due to the mass histeria over trying to find the Nintendo Wii, Nintendo is desparately trying to increase production from their planned 1.2 million units a month. They have stated before that even at 1.2 mill, this was supposed to be a very aggressive plan. Nintendo has completely underestimated the demand and now people are scrambling for the Wii.
They are having an amazing year, but the big problem now is that Nintendo Wii is potentially losing a lot of business because people will end up buying the Microsoft XBOX 360 and the Sony Playstation 3. The problem isn't really with the console itself, but it is with the games. The money is made from game sales and Nintendo will also lose out of those.
Nintendo has now increased the production to 1.8 million and trying desparately to meet demand. It is most likely that people will need to wait almost 3 months after Christmas to get their Wii.