Bar Code Switching
A particularly clever form of retail theft — especially when salesclerks are working fast and don’t know the products — is to switch bar codes. This particular thief stole Lego sets. If you know Lego, you know there’s a vast price difference between the small sets and the large ones. He was caught by in-store surveillance.
EDITED TO ADD (6/12): I posted about a similar story in 2008.