Loads of people have said a lot of great things. John Scalzi has a great conversation going on over at his kickin' blog. I just wanted to put in my two cents.
The thing I want people to take from this debacle is that Amazon is NOT for the consumer. Let me say that again: AMAZON IS NOT YOUR FRIEND. Amazon is a business. They want to have the lowest prices in the market so that they can muscle the other competitors out. Once they are selling the majority of all books, then they can negotiate more favorable terms with publishers. Right now they're selling 9.99 books at a loss. That's not sustainable. But it doesn't need to be. It just needs to last long enough for them to force publishers to sell them books for even less.
No matter what Amazon says, they're not standing up to Macmillan in order to keep book cheap for the consumer. They are not David, and the big publishers are not Goliath. Because, guess what, Macmillan isn't your friend either. They, too, are a business. They already work on razor thin margins, and they're doing their damnedest not to dilute the quality of their product.
Now, I know that there are lots of people who believe that any e-book above 9.99 is ludicrous. I happen to agree. However e-books are not publisher's primary source of revenue. In an e-book only model, a lower price point will reflect the lowered cost of doing business. However, right now e-books are part of the package that help offset the cost of printed books. So maybe we'll be there one day, but that day isn't here yet.
The other reason a price point above 9.99 doesn't bother me is (aside from higher royalties for me) is that ebook prices will eventually settle at a price that the market will tolerate. If a big book from a famous author comes out and the publisher prices it at 14.99, then people who really want it, will buy it. Many will not. And if enough people don't buy it, if they wait until the price drops, eventually publishers will adjust their prices to the appropriate price point. That's the free market. Publishers are allowed to set any price they want, and we are free to buy, or not to buy.
So to summarize: A publisher frightened by the future + a dick move by a huge retailer = No good for the consumer.
If you want to let Amazon know that they shouldn't pull these kinds of moves, then show them with your wallet. The same goes for publishers. Because the only person looking out for the consumer is the consumer.