Kindle Fire put them back in the ball game for tablet devices. While the Android-powered Fire isn't in the same league with the iPad in terms of design and power, it's rock-solid integration with Amazon's Kindle platform gives it a strong leg up in the ereader market - at a price-point that beats Barnes & Noble's Nook device.
Amazon, like B&N before them, has been pushing the benefits of a full-color reader over a b&w e-ink display - and selling the device at a loss to pull in those customers. To sweeten the pot, Amazon recently announced an exclusive deal with DC Comics for large backlist of digital graphic novels to be available only on the Kindle. While the LA Times reports that the deal is more of a "Kindle First" 4-month exclusive, the move was more than enough to invite retribution from Barnes & Noble.
B&N's response was to order their brick-and-mortar stores to pull the physical copies from their stores. B&N has maintained a strong position in the wake of previous Amazon or Walmart-exclusive deals to protest the move. If a publisher intends to do any type of business with Barnes & Noble, they are told that if they want B&N to carry their titles, the publisher must make all formats available to B&N that are available anywhere else. Thus, publishers pushing Kindle-only digital versions won't find a home on B&N shelves for their print copies.
Even Amazon has previously buckled on this issue - promising that titles from their own publishing imprints will be available in Nook format as well as Kindle in order to get those titles carried in B&N stores. DC either wasn't paying attention or thought the deal to sweet to pass up but B&N refused to look the other way.