Anyone shopping for e-books in the coming months would do well to check out the EFF's handy guide to the various readers and book stores' privacy pros and cons. It rates Google Books, Amazon Kindle, B&N Nook, the Sony Reader, and the FBReader on what info is collected, who it's shared with, and what control (if any) users have over their reading habits.
One particularly worrying quote:
Amazon's wording — "information related to the content on your Device and your use of it" — reads so broadly that it appears to allow Amazon to track all content that users put on the device, regardless of whether that content is purchased from Amazon. Some security researchers have indicated that the Kindle may even be tracking its users' GPS locations. Is this the future of reading?
It's a great resource, but it misses a key question for anyone planning on building a digital library. Which book stores and devices allow the vendor to reach into your e-book and delete books you've already bought?