To conform with Switzerland's strict privacy law, Facebook could be required to contact people whose information has been posted online and ask them whether they agree to its being stored there, he said.
So, tricky. Suppose this works. Then what? Facebook, let's say, removes the tagging in photos for people who aren't users of the service.
Which, frankly, is almost no-one.
In return, no other service can ever build up the inertia facebook did, because you can barely use it till you persuade all your friends to sign up to the new one.