I’ve heard that explanation a few times but I find it very hard to believe that's the primary reason. I can't imagine Costco would devote two workers full-time to that -- it’s simply against their lean philosophy.

That's the second reason I find the practice so irksome: on top of requiring customers to wait in line to prove their innocence, they pretend that the practice is for their customers' benefit. And people believe them!? Maddening.