I can only comment on my local Whalemart, but they have been putting in more and more locked display cases for expensive items or even cheaper items that are popular with thieves.
Some shelves in the health care areas (supplements, pain relievers, etc) are now protected by clear plastic doors hinged at the top that you have to lift up to get to the product. As soon as you lift one of those doors, a friendly electronic voice thanks you for shopping at Walmart, and if you keep the door opened too long, the friendly voice changes to an annoying beep that gets progressively louder. I haven't been able to locate the cameras behind those doors, but I know they're there.
I'm not sure how much these measures help, but I suspect they only keep honest people honest.