The Home Depot and Giant in the town I grew up in now have anti-theft devices on the carts to keep people from leaving with them. Was kind of surprised in Giant's case because you'd have to cross a highway intersection to get to a sidewalked area, but I guess people are determined.
On the other hand, the Walmart right next to my parent's house did nothing but put two concrete columns close together on the sidewalk exiting the back of the parking lot. As if people weren't just going to push the carts around them