Folks, don't panic. While I have *no* specific WD-related facts to present, I do work in an industry that is similar.
The issue is probably simply that first-tier distribution is just sold out.
Contrary to popular belief, factories don't just spend all their time making a single specific product.

The WDTV isn't like an iPad that can keep a Custom Electronics Assembly/Manufacturing plant fully utilized.
WD probably orders some larger number of units at a time and then sends them to 1st tier distributors, and then the CAE goes on to making someone else's products.
If there's a run on them (think Christmas season) and distributors start running out, then what you're seeing now happens.
2nd Tier distribution and retail retail starts going out of stock, so vendors start showing out-of-stock, while other vendors' distributors still have them available.
it could be that distribution didn't anticipate the demand, and orders are now sitting in a CAE company's queue somewhere waiting to manufacture more. It can take MONTHS to get to the head of the line and get the 1st tier distributors replenished.
Amazon changes pricing constantly, based on demand. I've seen prices double between the time I've placed an order and the time it ships the next day. (Example: Bought a DVD set that was $59, and the next day, it was $109. From Amazon, not an Amazon partner.)