Did you notice that this year there is no real must have gift or new hard to find toy? Sure the Wii is yet again not that easy to find, but that has been the situation for three years in a row now.
Even the new Elmo is still very easy to find and even got put on sale. If you go by how much premium you have to pay to get your hands on a specific gift this year than the Amazon Kindle is the winner (besides the Wii). As reported Kindle is sold out way beyond Christmas. If the high demand is Oprah's fault, or it is just poor supply management by Amazon again, is not obvious yet.
On eBay a sealed Kindle eBook reader sells for about $450 instead of the $359 it supposed to sell on Amazon. The markups are actually still not as high as they could be. In a different economy the markups might be at double the MSRP as it has been with hot gadgets and toys in the past.

Whether the lack of a hot must have item or the economy is going to be the bigger reason for the holiday sales decline is going to be hard to determine.