To our eyes, these seem like small things. But, it would likely help a publisher to collect pre-order data for certain books to gauge demand, plan marketing, and ramp up resources for forthcoming books.
The bigger picture is that it's illustrative of the enormous power Amazon has in the book world. The New York Times says Amazon is trying to extract better deal terms from Hachette on e-books. As part of the negotiations, the NYT says Amazon is doing stuff like this, and was previously delaying sales of Hachette's books.
Amazon has tense relationships with publishers. As it collects more and more power, it continues to try to extract favorable terms for itself.
Oddly, Amazon has gotten the government's blessing on this, in a way. The Department of Justice ruled that publishers were colluding with Apple to raise e-book prices. This has let Amazon get even bolder in the e-book market.
We emailed Amazon for comment on this, and if we hear back, we will update this post.