For the stores I'm not sure this will be a good thing - in fact I hope it's something we don't see except perhaps for high value / cutting edge items as things are pretty rough in the world already.

One thing for sure is that we have to be very careful how we apply any new and novel advances as people (rather, companies) tend not to think through the consequences when money is the prime motivator.

I don't want my last meal turning bad as the supermarket found my card was invalid after I left the store, leaving me in hospital racking up another bill for food poisoning...