In places like CA, this is heavily implemented. There's a little magnet under the street, that when you push the cart over the line... the wheels lock up, making the cart much harder to steal. It's effective. The wheels lock, and you'd probably bust your head open trying to get the cart to go over the line.
It may sound... like a complete and utter waste of money. But, these shopping carts cost anywhere from $100-$150 a piece. And with some stores reporting weekly losses of carts, in the double digits, it only makes since.
It's also a luxury for people retrieving carts. No finding carts across the shopping center or, in some nearby field. They lockup, before it happens 🙂