When I think about privacy I like to think of it in two terms. Granted privacy and real privacy. Granted privacy is when your neighbor agrees not to look into your window. Real privacy is when you buy curtains. That’s a good way of looking at this excellent post by Vikram Kumar about the privacy of Amazon purchases. Amazon, like most large retailers, will do their best to protect their customers privacy. But this is granted privacy and there are numerous situations (some outlined in this article) in which that grant will be revoked. All the big vendors do business word-wide in many countries with different and often conflicting privacy laws. Past experiences has taught us that some vendors will cough up their customers private information merely for the privilege of business in China.
In a nut-shell, Amazon will grant you privacy so long as it doesn’t conflict with the laws or dictates of a country that they want to do business with. If you want real privacy you have to drive to the bookstore and pay cash.
On a similar subject there is this interesting article about privacy concerns on Google’s upcoming Gdrive service. Unless Google incorporates some pretty strong encryption (with user managed keys), anything you store on it will have only granted privacy. Of course in the US the government can always search your computer disk drive if the get a search warrant. The big difference is that a search warrant is harder to get than a subpoena, it usually requires a criminal investigation, and you would typically know about it.