I've been to at least 3 Sainsburys where there is a camera and screen facing you at the self service check out.
If anyone objects to this invasion of privacy, my advice is to turn the camera and screen sideways as it's mounted on a pole.
I'm curious why you think this is so egregious an invasion of privacy, when you're on camera virtually everywhere in any store anyway. At least with these ones you can see what the camera is picking up. (And yes, there were protests when they first came in because, depending on angle, they could pick up the PIN entry pad on the card reader, but there's a black box over that area on all the ones I've seen lately.)
Presumably the cameras have been brought in because some people can't resist the temptation to fiddle the system, which is really just shoplifting by another nametheft.
I think there's a fair bit of research that shows cameras are a bit of a deterrent, but it's seeing yourself on screen that *really* puts thieves off. Hence (at least in our local store) visible screens in the booze aisle and near other high value/easily concealable/easily resellable items.
I can't help thinking we should all be against replacing actual human jobs by the customer having to do it themselves. If everyone queue'd for the actual human, shops would soon abandon this stuff.
I agree to a great extent with your first sentence - it's yet another way companies are finding to externalise their costs, though checkout operation is i) tedious, ii) highly measured, and iii) pretty crap ergonomically, so I'm not sure we should have a great campaign to save those jobs in particular. But staff costs are an obvious thing for retailers to try and cut, and as a nation we seem to be so bloody obsessed with the cost of food to the exclusion of almost any consideration of quality, or of service, that I can't see self-checkouts disappearing any time soon - one assistant supervising six or eight or two dozen is a *lot* cheaper than having that number of tills open. (Plus, of course, some people actually prefer them, either because it's a shorter wait, or because you don't actually have to interact with another person when you use them.)