While the Zune still pales in comparison in terms of hardware to the iPod, Microsoft has still seen relative success with the unit. Enough so that they have released various new iterations of the unit, such as the 80GB unit with an internal hard drive. That unit, however, has been hard to find - much harder than its other brethren, and Microsoft is blaming that on popular demand.
As the 80GB unit was fairly well received, that's not good for Microsoft. When larger retailers like Amazon, Best Buy and Circuit City aren't able to keep the shelves stocked, the unit might as well be vaporware. According to the article, there are rumors of the 80GB Zune being six weeks behind production schedule. Could Microsoft be facing supply issues? If so, why the 80GB models and not the flash-based models as well? The article also cites Microsoft claiming they focused on the 4GB and 8GB units at first, which resulted in the larger capacity models being pushed a bit to the back burner.