There used to be a commercial a few years ago that had a guy walking around a grocery store and stuffing his coat full of goodies.  You were meant to believe that he was a shoplifter but, when he walked out the door, it was shown that he was a customer taking advantage of some new technology that allowed his items to be scanned and purchased without going through a register.  I don’t remember who the commercial was for but it sounds like a neat idea.
But…  How would you buy produce that was required to be weighed?
We’re not quite there, yet, but there are many stores now that have self checkouts.  While I’ve grown up in the computer age and can adapt quite easily to new technology as it shows up, I find myself not liking these things at all.  I usually have problems of some kind as I use them.  I don’t always know where the problem is when the system demands that I call for assistance.  Most of the time it appears to come with the bagging.  These systems don’t like it when you remove the bag from the area, and they certainly don’t like it when you have something that’s too big to fit in a bag.
They also mean less jobs for cashiers.  Another problem I see is that, since they have less cashiers and many people don’t like the self-checkouts, that there are longer lines when you want to deal with a human.  Combine this with only one person to help with the check outs that go awry, and you’re looking at an increased time trying to check out.
All in all, I think they are quite a nuisance, except when you’ve only got one or two items you need to purchase.