PDFZone reports that Adobe's Digital Media Store will soon shut it doors (Adobe to Shut Down Digital Media Store). Adobe spins this as due to the success of selling e-books through other websites such as Amazon, but an analyst has another take:

"There aren't the same production costs involved, [yet] there is usually little or no difference in price between e-books and their physical counterparts. And the physical book format is highly portable. You can lend to someone else, while e-books are constrained by the devices they can be read on. It's hard to share content [through e-docs] as it is with physical books and magazines," Wilcox [a senior analyst at Jupiter Research] said. For his part, Wilcox said he is baffled that e-books didn't pursue a lower-cost strategy to increase their adoption.