They speculated the "why."
this is so confusing in the Nintendo sold 1.2 million hardware last week thread no one believes the thing is sold out many report seeing some around. But now GamStop is cancelling the waiting list program because they cannot get a new shipment?
And they also quoted Reggie's "nearly sold out" statement.. which for the most part, people know to be an exageration.. considering the plethora of Wii-U's available at retail.. also evidenced by the Ebay prices for the thing.. which are only getting $25-50 above retail.. many aren't even selling at "Buy it now" prices in that range.
However, likely due to the extreme demand for the system, local GameStop management has confirmed that company is discontinuing the waiting list.
GameStop COULD BE having supply problems themselves.. but that would be because they are just one of many retailers.. and probably the main retailer for Pre-orders.. but that hasn't really been verified.
They might have cancelled the "waiting list" SKU because so many people on the list had already purchased a Wii-U from one of the retailers that have had plenty of stock for instance.. so no new "waiting list" customers.. the entire point of that is to just have good customer service.. I wouldn't be shocked if GameStops were just telling people to go to another store.. they are pretty cool like that.. I've had GameStop managers inform me that stock was plentiful elsewhere for various items.
edit: I'm seeing others claim that they've called GameStops who have told them they have several Wii-U's in stock for sale.. could also be why the waiting list SKU was cancelled.. plenty of stock.