And what happens when the criminal class discovers that the $18k/year greeter near the store entrance will do nothing? Why will this be a remotely useful deterrent in that case?

Consider the possibility that if the greeters actually prevented a significant amount of shrinkage, walmart would have kept them. The cases being referred to the cops are only a tiny percentage of the shrinkage that occurs.

"Consider the possibility that if the greeters actually prevented a significant amount of shrinkage, walmart would have kept them."

It's a possibility, I guess. But I've seen enough MBAs cut costs with poorly understood consequences to be a little skeptical of that assertion. How would they even know? Did they run a controlled experiment? Or did they just say a prayer to Jack Welch and cut anything they could?

It seems they've been running the experiment over the last decade? An executive will never get fired for cutting costs. Even if the cut costs destroy the company, she'll be off to greener pastures before that happens.