ePub books with Adobe's DRM is pretty device independent. Currently I can buy a book from Sony bookstore, B&N bookstore, Borders bookstore, or fictionwise.com and load them onto my Nook. I could also load them onto a Kobo reader, a Sony reader, a pandigital novel reader, etc.
Amazon.com books can be read on the kindle.
iBooks can be read on the iphone/ipad.
It's clear who gets it--Adobe, B&N, Borders, and some other small time people (pandigital, kobo, etc)
However, EVERYONE wa