Ive had a Costco membership for at least 12 years ( since my daughter was born) and they didnt have the inspections up front. They were notorious about not checking all my items out at the checkout. Seriously, when there was only one cashier by themselves, they would miss my water almost every time in the bottom of the cart. I was getting overloaded with paper towels that I never paid for, clothes not scanned, you name it. Then they must have done an audit and realized how much they were losing. I remember very well when they started to put tag teams on the registers to help out. Then the security was set up to triple check the accuracy. Still, they miss stuff and security catches it.
As for Best Buy and their ilk, they cannot forcibly stop you for just a random check of your receipt. They have to have a reason, like they observed you pocketing that Gay Cowboys in Bondage deluxe Bluray DVD, otherwise you can get them in serious trouble. I walk right past them all the time and the guy will say " Sir, we need to check your receipt" and I say no you dont. Never, ever, been stopped because of that.
Peace
Lounatik