Complexity. A policeman taking a literal print of your body is far simpler and more direct than "big data" and so on. Remember that most computer users are haz

Complexity. A policeman taking a literal print of your body is far simpler and more direct than "big data" and so on. Remember that most computer users are hazy at best about whether `natwest.my-account.co.uk` is a phishing scam. There isn't the necessary baseline of informed opinion to have a reasonable discussion about this kind of snooping.