A handshake and a smile?

From Boing-Boing, an article on an FBI proposal for unnerving would-be bank robbers with kindness.

What's the best way to make a bank robber turn around and walk out the door empty-handed? Try a handshake and a smile.

I can see this model working against identity hackers and thiefs. Make your protocol so inviting that they turn away either out of courtesy or because they suspect a trap.

There are even existence proofs.