I agree it can be very helpful. But also scary. Just something to keep in mind so you don't walk blindly into a big data pool. If you are aware of what the companies are doing and choose to do it anyways, that is fine. Not knowing is bad no matter which way you cut it.
Hmm...I think the problem is the boat has already sailed. If you have a credit card, an email account and a mobile phone you're already fully integrated into the big data pool, and there's not much that cannot be tracked about you. Adding in an Amazon account is not going to provide any more raw data that isn't already easily and instantly available to anyone with the right connections. The only way off this vessel is to sign out completely, cut up your cards, delete accounts, go offline and ditch the mobile, with all the attendant inconvenience that entails. This is our world nowadays, good and bad.