Apparently this is a true shortage. And it makes sense: this is the biggest shopping season in the year. Why would B&N "create" a shortage of a popular item during the time of the year that it's in the highest demand?
There is
an illuminating post about this on the New York Times's "Bits" blog. They quote an analyst as saying that B&N and Sony rushed the announcements of their respective wireless devices. The companies announced the products well before they were ready, in order to show that they could compete. I found the follow-up quote from Amazon particularly amusing.