Slate has a new article,
I Want It Today, that argues that Amazon's change of heart on sales taxes is associated with their plans for same day delivery in densely populated areas of the US.
A comment at Hacker News suggested that this will end up as a battle between Walmart and Amazon. The B&N vs Amazon ebook example suggests that brick a mortar companies can survive for a while, but I would not bet on B&N being around in five to ten years.