The Official Dec 2009 NPD Thread (Data for 5 weeks ending Jan 2 in 5 hrs)

[Khuutra]

Demotruk said:

Then perhaps Walmart had shortages resulting in NPD overestimating their Wii sales, or something.

This is very possible

It's also possible that Nintndo just wanted to see the internet explode on NPD day.

Like Brett said: wait for Nintendo's financials.