This comes from a CCTV Facebook Group. I thought it was interesting:
The poster wrote:
"I saw this camera/monitor thing in the tools department at Home Depot. It had what looked like pre-recorded webcam feeds of people watching camera feeds in the corner. We tried waving but they didn't wave back. Anyone know more about them? Looks like an desperate attempt at theft deterrence."
Notice, the OP says this 'looks pre-recorded', so the deterrence may be short lived once the thieves figure it out.
However, I actually think this is a pretty smart move, to show a picture-in-picture inset that shows someone is watching the cameras. It's presumably low cost/free to add to the existing install, so why not?
If your public displays included a live output stream of monitoring staff, would it be good or bad?