Where is the Xbox 360?

From the NY Times:

In fact, those looking to buy an Xbox 360 may be out of luck. It is largely unavailable now, and the few that can be had are fetching double and triple the $400 retail price from online stores and eBay.

Now, either Microsoft woefully underestimated the demand for the new Xbox 360 (although I very much doubt it), or they're up to something. But what?