Actually, depending on the sales figures, the books being sold at $9 can have a huge impact on B&N and Borders. Four of the books on the list are huge sellers in bookstores. The new novels by Stephen King (hugenormous), James Patterson, Dean Koontz, and Michael Crichton. These authors sell in the hundreds of thousands. Now, if you can get the book for 70% off with free shipping, and no tax, of course you are going to. $9 is cheaper than the new over-sized mass market paperbacks (that suck) that are being printed now-days. Bookstores wont sell their copies for more than 50% off (which in itself is a loss). So, imagine all the people who would normally buy at B&N going to amazon and walmart instead. That is that many customers that won't be going to a bookstore anymore.
Real world example:
When Harry Potter 6 came out, my bookstore had 20% of our preorders cancel because the local Walmart was selling the book for 50% off, and we were selling it for 40% off. That small extra price off reduced our sales a TON. Now compare a bookstore selling King's new novel at 40% off vs. Amazon at 70% + off (they could still go down even further). Now factor in the economy. Yeah, this could seriously hurt bookstores sales, who typically make their sales plans taking new releases into consideration.
A part of me is glad I get the books for insane cheap, but another part see this as just another sign that physical bookstores are going the way of the dodo.