According to Stan Veit (author of History of the Personal Computer), this has been a pretty common tactic for computer and console manufacturers from the beginning. The strategy works something like this. The stores (Sears, Wal-Mart, etc.) know that they'll only be getting a small fraction of the units they order, so they order far more units than they need. Meanwhile, the manufacturer takes all of these funds and uses them either to earn a quick profit (stocks go up), or to fund the production. The manufacturer then sends out the first wave of units and then lets supplies stockpile in the factories. Finally, the manufacturer unloads the merchandise in bulk, and stores that ordered way more than they can sell (particularly if the product fails in the marketplace) are stuck with a huge inventory and have to unload it at a loss. It's a win-win situation for the manufacturer, but the stores (and the gamer) gets screwed.

There are even cases where a company didn't have the facilities to manufacture the product until advertising and accepting huge orders (and pre-orders), then using that money to pay for the process. Just imagine!

Nintendo and the rest know that stores are desperately trying to get these units on the shelves before the big holiday season, and they'll end up ordering so many units that they'll have to get rid of if the unit flops.