I think their IPs will start getting blocked if they substitute ads. However, the Kindle ads would work wonders. Just inferring the main categories in which the

I think their IPs will start getting blocked if they substitute ads. However, the Kindle ads would work wonders. Just inferring the main categories in which the user makes purchases from their Amazon history and showing the top five best sellers in those categories would be sufficient, but having the web history is huge. That said, the potential abuses are also massive if they start getting hit by warrants/national security letters.