Amazon is solving a problem that the individual author or reader does not share: they are making the delivery of books more efficient to the marketplace.
Books are in a strange place because the time invested consuming them far outweighs the equivalent cost of purchasing the book. I am not limited by price to the number of books I can consume each month; I am limited by time. Already many readers end up buying more books than they can read. In addition, free books are available at this place called the library.
Music, movies, and the rest of digital content is not like this. You can pick up a video game and play it for an hour, then put it down. (In fact, the stats show most apps are only used a few times, then never used again)
In an author-reader relationship, the author is trying to provide enough value for the reader to spend dozens of hours and many days consuming the material -- and more to the point, the express purpose is to somehow change the mindscape of the consumer. Good books require lots of time and change the reader forever.
So what Amazon is effectively doing is destroying the concept of reading by making it nothing more than an extended version of an mp3 song. But since you can't just consume a book in 3 minutes, more books will be sold and more books will remain unread. Books -- long form content -- will become superfluous. It's all low attention span, immediate pleasure consumption now. I imagine we'll see more and more readers buy an ebook and read a few pages and stop. The nature of reading will change.
And while this might result in more overall book sales, it doesn't do much for the individual relationship an author has with a particular reader.
There's nothing wrong with making books like every other form of digital content. Everything is bits, and bits gotta be free. But as a consumer of good books, Amazon does not have my best interests at heart. It's just playing a numbers game. My best interests actually might be books that cost 100x what they currently do: make me feel some pain and spend some careful thought about what I'm going to spend my time on.
I am not interested in delivering the maximum number of unread ebooks to the most number of non-readers. I am interested in choosing those 5 or 6 books each year that are worth my investment in time to experience. And as an author, I am not interested in maximizing sales. I am interested in maximizing impact. Amazon is friend to neither of us.