re: Why doesn't Walmart call the police on shoplifters after they leave the store?

I practice in criminal law and I can tell you that (at least in GA) Wal-Mart takes shoplifting very seriously and has spent money on the best surveillance equipment I have seen.

I would hazard a guess that more than 75% of the shoplifting cases prosecuted locally come from the Wal-Mart. That is not the only place being hit, but it is the one place you are likely to be caught and prosecuted.