Facial recognition is digital alchemy. It's the prince of data mining.

Facial recognition takes previously anonymous images and conjures peoples' identities. It's an invaluable capability. Once they can pick out faces in crowds, trawling surreptitiously through anyone and everyone's photos, the social network businesses can work out what we're doing, when and where we're doing it, and who we're doing it with. The companies figure out what we like to do without us having to 'like' or favorite anything.

So Google, Facebook, Apple at al have invested hundreds of megabucks in face recognition R&D and buying technology start-ups. And they spend billions of dollars buying images and especially faces, going back to Google's acquisition of Picasa in 2004, and most recently, Facebook's ill-fated $3 billion offer for Snapchat.

But if most people find face recognition rather too creepy, then there is cause for optimism. The technocrats have gone too far. What many of them still don't get is this: If you take anonymous data (in the form of photos) and attach names to that data (which is what Facebook photo tagging does - it guesses who people are in photos are, attaches putative names to records, and invites users to confirm them) then you Collect Personal Information. Around the world, existing pre-biometrics era black letter Privacy Law says you can't Collect PII even indirectly like that without am express reason and without consent.

When automatic facial recognition converts anonymous data into PII, it crosses a bright line in the law.