It appears that Christopher Null, a blogger/columnist for Yahoo! News is collecting all the theories for why the Wii is as yet unattainable by most folks. From supply and demand to "Space Aliens are using them as a means to control the population so the government is limiting the units to protect mankind from invasion." (ok I made that last one up)
Among the more reasonable answers: Big Box Retailers are hoarding them for sales.
The Most far out: An army of lawyers are preventing Nintendo from fielding the units and All the units are going to A-list NBA players first for free.
I've seen some interesting analysis elsewhere but Null's entry doesn't really analyze anything - it just gives us all something to chuckle about.
His entire column is located here