How does it differentiate between a shoplifter stood next to you and someone who is helping with the shopping. If a shoplifter follows you around and leaves with you, do you get charged for what has been nicked?
From the video, it appears to be necessary for customers to touch their phones on an entry terminal, to log them into the system - much like the way I use a card to log myself into the London Underground system.
The difference in the Amazon store is that there don't seem to be any turnstyle barriers, as there are on the Underground. I imagine there will have to be a beeper system that sounds if someone just walks in and takes an item without logging in.
There are going to be teething problems, but I like the concept very much. Anyone who has used a busy Pret a Manger store on a weekday lunchtime will know about the delays that can arise at the checkout. The Amazon system would put an end to that.
The technical wizadry starts when the store has to track individuals, so it knows what to charge to which account. Imagine a store with fifty people, all taking stuff, putting it back, leaning across each other to pick items from shelves, and generally criss-crossing the floor. It's easy to track phones in and out, but tracking each phone in a constantly moving crowd, and knowing which person takes what from where? It's a nightmare scenario.