We've heard about Sony intentionally relying on more than one company to manufacture their PlayStation 3 units. Despite that, could they still be facing a severe shortage, one that may prevent them from reaching their shipment quota? Originally committing to ship 6 million units by March of next year, 4 million of which would be shipped this year, they are now saying they may only get half that:

Sony earlier said it would only be able to ship 400 thousand of PlayStation 3 game consoles to the U.S. and 100 thousand to Japan for the launch in November, 2006. During the whole calendar year 2006 the company aims to distribute, according to news reports, two million new-generation consoles, two times less than anticipated. But the company does not seem to be sure it would meet its “targets”.
They will be only using Asustek to provide units this year, but the problem does not appear to be an inability to manufacture them fast, it appears to be a supply issue. Primarily, they are citing the inability to manufacture a decent amount of Blu-ray devices, a problem they had hoped to solve but were unable to. One problem consoles have seen the past years upon release is people hording them and reselling for much higher than retail. Given the already high cost of the PS3, lowered shipments will only amplify that problem.