There's some information about what the Kindle reports to Amazon here:
https://www.mobileread.com/forums/showthread.php?t=51371
I'm assuming the GPS co-ordinates are just for the 3G version, but the rest of it is pretty scary too. Whoever it was said that Amazon doesn't know what you are reading and how quickly you read it obviously hasn't seen that thread. They also log whether your books are encrypted or not.