Actually, there's a bunch of facts mixed into one big fact that's somewhat false.
Fact - Microsoft has ordered retailers in Norway that they *MUST* sell out of consoles *ON RELEASE DAY*. Otherwise they will not ship them units. (Other related facts - each store will get 20 units - 14 "premium", and 6 "basic", and each console must go out with at least 2 games each)
Fact - Microsoft has put a bunch of retailers "on allocation". Which means that even if they have 100 units on preorder, they may only get 10. These retailers are almost all exclusively game stores and some electronics stores.
Fact - Microsoft has more than enough capacity to fulfill all pre-orders. In fact, they've ordered their production lines *SLOWED DOWN* to crank out less Xbox 360's than if they were running full tilt.
The first fact is irrelevant as North America's going to be the Xbox 360's largest market (Japan usually is, but given feeble Xbox sales over there, I doubt Microsoft would be dedicating very many units there). There are also rumors that sales aren't as high as Microsoft would like (number of pre-orders is less than anticipated, hence the possibility for forcing an artifically low supply). Ditto with the "on allocation". In fact, it's quite likely that if you really wanted one, line up at Wal-Mart and buy it there rather than GameStop/EB. Or anywhere else you see carrying consoles that you traditionally don't associate with gaming. But Wal-Mart would be the retailer with the stock since they have the power to tell Microsoft to "shove it" if they don't get their order. (Wal-Mart is king, and Microsoft *will* supply them first.)
Now, taking the fact that Microsoft has slowed their production lines down, plus that the Xbox 360 is a near-simultaneous release worldwide (Norway was December 2nd or so), could it really be it isn't selling that well?
I'd say your best chance at getting an Xbox 360 would be to go to Wal-Mart.
Edit:
Let's add some references.
Xbox 360: Retail Bully -
http://www.gizmodo.com/gadgets/home-entertainment/xbox-360-retail-bully-134320.php (conditions for selling Xbox 360s in Norway).
Xbox 360 Tests Its Brakes -
http://www.gizmodo.com/gadgets/home-entertainment/xbox-360-tests-its-brakes-134098.php (Microsoft to slow production of Xbox 360, and to not spike production during holidays to meet demand.)
Xbox 360 to be in short supply -
http://www.gizmodo.com/gadgets/home-entertainment/xbox-360-in-short-supply-130969.php
Ironically, I pasted them in reverse-chronological order. Amazon stops taking pre-orders, then Microsoft won't spike production to even meet pre-order demand, followed by retailer strongarming? Yowch.
Me, personally, I haven't seen any xbox 360 game that looks good - mostly sports (ick) and FPS-type games. Nothing compelling, and the emulated list doesn't include my favorite Xbox games. Maybe mid-2006 when the mass of Xbox 360 games are supposed to come out.