This goes contrary to the degree of control Amazon likes
Forcing an "agency model" on any retailer is going contrary to both history and market standards. The general model for booksellers is to buy wholesale, at somewhere around 40%-50% of MSRP, and then sell at some price between that and MSRP. Amazon has discounts of MSRP all the way from 55%, to only a few percentage points. Barnes & Nobles has similar prices (if you become a "B&N Member," for US$25/year, the prices are pretty much the same as Amazon's. A bit lower sometimes, a bit higher sometimes.)
What's really going on here is power: the publishers have decided they don't want retailers undercutting each other -- that leads to a single player having market dominance, which allows them to try to force concessions (lower prices, content changes, etc.) from the publishers. As examples of this, see Amazon and Wal-Mart.
When Apple joined the ebook market, however, they were able to take the same "we don't care about making a profit on content" attitude they have for music, and offer it to the publishers. And the market share Apple can offer with the iPad is probably at least as large as Amazon's current market share with is Kindle. (And unlike Amazon, Apple won't be paying the end-user bandwidth costs.) This gives publishers who are willing to sign up with Apple enormous negotiation power with Amazon -- over ebooks. Amazon's only negotiation power that can counter that is the physical book market.
Personally, I would certainly be offended if someone said, "You will sell this product at a price we dictate, and only take 15%. You cannot charge more to make more money; you cannot try to maximize profits through selling more by offering it for less. And if 15% of an arbitrary price we set isn't enough for you to make profit -- or even enough for you to run your business, tough." And I'd fight it as best I could.
Of course, that's also pretty much Amazon's attitude towards the publishers. So a pox on all of them, really.