E-Book Buyer’s Guide to Privacy – Electronic Frontier Foundation

Since then, thanks to the feedback and corrections we've received, we've made some updates and corrections to the guide which we hope will make it more useful. First, we've re-written many of the questions and answers to provide more clarity about the behavior of each e-reader. Second, we've tried point out where companies' privacy policies themselves are unclear on particular issues. And finally, we've made the whole thing easier to read by changing its visual layout.

via Updated and Corrected: E-Book Buyer’s Guide to Privacy | Electronic Frontier Foundation.

They had one a few weeks ago, but this has been updated. If you are deciding purely on privacy reason, the FBReader is the best.