Reading this interesting post on publishing on Kindle reminded me of something. You mention that Amazon controls a vast amount of the book publishing market. The Kindle format is not open, so the only way to buy Kindle books (that you read with your Kindle Reader app) is through Amazon.

Once-upon-a-time this would have been a recipe for an anti-trust lawsuit. The government would have a pretty strong case and would, at a minimum, force Amazon to open up the Kindle format and the ability to load books from another source.

However, if you're Jeff Bezos and want to escape this fate, all you have to do is suck up to The King (along with some financial donations). The US Justice Department is corrupt and will not go after anyone that The King doesn't want prosecuted.