The Albertsons just up the street here in Frisco, TX already uses a similar system.

Every cart has a holder for a scanner. You run your loyalty card at the scanner kiosk near the entrance and it issues you a scanner. You set up the bags in your cart. Then you scan each item as you go.

I'm not sure how they prevent shoplifting. The biggest problem seems to be lack of use. My wife uses the system when the kids are with her because they think it's fun and it saves a little time. I never use it because Albertsons is just the convenience store to me, if I'm doing serious shopping I go to either WalMart to save money or Central Market (HEB) to get the best quality produce and meat. I've never seen more than a handful of people using the cart scan system at one time.