Seriously is this 2007 here... I have not been following Vgchartz much now for about a year. But the last time I remember the Wii having a shortage issues was during the Holidays (and post holidays) 08. I have not gone out seaching which stores near me have it or not, but Both Walmarts near me, target, and at least 2 gamestops did not have any Wiis.

Is it because of NSMBWii, or did Nintendo cut production too much when sales slowed down last year?

Because nintendo cut downed production after a record breaking holiday. Nintendo under estimated the wii like always

Simple. Nintendo isn't shipping enough to meet consumer demand.

Kinda what yoshi said. Sales in the first half of 09 were down rather significantly from 08, so production was reduced. However, December came along and blew away sales records, forcing Nintendo to airship some of 2010 Q1's Wii's to retail for the holidays. However, this means that Nintendo doesn't have the reserves to replenish retailers now, and as such, are shipping them out as they make them. I don't know if Nintendo's trying to ramp up supply again for a few months to have another safety cushion or not (though I think it'd be good if they did), but it's forecast to go through at least the end of March...

wow, Nintendo really needs to fire their planning and logistics teams... lol

Because the wii is a virus!.....................................or pretty much what everyone has explained already about it's current production value.

...and now they are selling a quarter million Wiis worldwide each week due to extended demand from the price drop + New Super Mario Bros Wii and increasing demand in Just Dance....(That last part is only personal theory)

I consider it a good thing. Too much Wiis lowers the demand. 

You just gotta hang in there.  

I think everything that anyone could suggest would be speculation because no one knows for sure ...

Personally, I wouldn’t be that surprised if there was a redesigned Wii coming out in the not too distant future. This change could be mostly cosmetic for sales purposes (smaller or colours) but it could also incorporate fairly major internal changes to prevent piracy. Before introducing a change like this, Nintendo might keep the supply chain tight so that there were (very) few "old-style" Wii systems remaining unsold prior to releasing the upgraded version.

A more substantial change might also be possible, and Nintendo could do something more in line with the "Gameboy Color" and try to produce an enhanced Wii of some form. If you introduced significant increases in piracy protection while producing a reason for existing owners to upgrade Nintendo could drastically reduce the level of piracy on the Wii. The most obvious possibility for a change like this would be a system that rendered Wii games at HD resolutions, but there are (probably) many other possibilities.

Note: For those that didn't know, in most ways the Gameboy color was identical to the Gameboy and the handful of "Gameboy Color" only games were not released on the Gameboy because color was needed to play the game. The reason I used this as an example is that I think Nintendo would want to keep any new system as being (basically) the same platform.

If the Wii has no shortages since it was launched I think it already could be reaching 75, more or less..