But it isn't a grey area: it simply doesn't work. It doesn't matter if it correctly identifies most people: it has to correctly identity most terrorists, and it

But it isn't a grey area: it simply doesn't work. It doesn't matter if it correctly identifies most people: it has to correctly identity most terrorists, and it simply doesn't do that, because if you are a terrorist you just keep rotating through IP addresses on cloud providers and VPNs until the entire service is burnt. It isn't that it sometimes doesn't work: it's that it doesn't work at all when it actually needs to work. We could argue that the services shouldn't let you do that in the first place, but the reality is that services currently do work like that, no one is trying to change that, and if they did try to change it we would all be even less happy with the resulting even-more-powerful surveillance state.