I remember seeing a commercial for something one time where somebody just pushed a cart full of groceries through a portal-thing, and it automatically found all of the items and their prices, by RFID or something, found his credit card in his wallet the same way, and auto-charged it for all of the groceries. If they had that, I'd do it.
The reason given is to be more "customer friendly", which seems to correspond to the upscale neighborhoods where the lanes are being removed and, not surprisingly, more upscale grocers are starting to move in (Roundy's/Mariano's, Whole Foods, Fresh Market).
Turns out it takes a lot of staff intervention to keep the self-checkout lines moving.
However, I'm not quite sure that will be enough for shops to automate. The problem for shop is that an automated system most likely cause of failure is to miss items. That added to the likely need to remove some security features to simplify automation and the already existing shoplifting problem means shop owner will be more interested in more clever (read more obnoxious) self checkout system than automated ones.
I'll actually wait slightly longer for the automated checkout at the market, mainly because I want to see it in more places.