Airport security makes passengers vulnerable to having their things stolen. They're forced to send their things out of sight and forced to look elsewhere while security officers scan them, all while potential burglars are free to take their possessions off the conveyor-belt at the end of the x-ray machine without question. And because passengers are rushed and stressed, the theft isn't necessarily intentional; sometimes people end up grabbing similar looking bags by accident.
In Singapore, officers place a placard in each tray that goes through the x-ray machine and give passengers a matching placard to carry with them through the metal detector. Then, to retrieve their bags they need to present the appropriate placard to prove that the contents of the tray belong to them. This simple design is effective in making theft more difficult while leaving throughput relatively unaffected.