If you do not create an account on the Hue website, Philips only keeps track of your Bridge IP address. The only reason they do that is so that your app can find it.
From the moment you create your online account, Philips also keeps track of the current status of your lights. They need to know this so that they can tell you if they are on or off or if they are set for a specific scene. The ‘Hue Terms and Conditions of Use’ will cover these topics in detail.