How we do things, throughout life, can be tracked. Our face, as well as our gait as we walk, our different actions on certain websites, and our shopping habits. This is another way we can be identified as individuals in a sea of billions.
Your iPhone can be uniquely fingerprinted by apps and websites in a way that you can never clear. Not by deleting cookies, not by clearing your cache, not even by reinstalling iOS.
Found at www.theregister.co.uk