Personally, I'm opting-out of the Amazon store, as I did the B&N and Sony store through Smashwords. As I already sell my books in formats that can be read on their readers... as I can fully control the look and formatting of the books... and as I can't afford the advertising costs that would bring my books to anyone's attention on those sites... I can't see the point of putting my books in there, to make one or two sales a year and only get 40% or less of the gross.
Not that I'm recommending that to anyone else, unless you happen to have a website of your own where you format and sell 5-6 formats of your own books. I'm just sayin'.