Apple's retail group is smart, and it knows that the best way to get someone to buy a product is to give them unfettered access to a device. Up until recently, that really wasn't possible as each and every device was tethered to a table with a security cable. If you wanted to try picking up an iPhone 7 Plus to see what it really felt like in your hand or pocket, you couldn't do it without that cable dangling from the back. Apple has removed those tethers now and replaced them with other security measure to insure that devices won't be walking out the doors of the stores.
Ben Lovejoy of 9to5Mac found out what Apple is using as a "virtual tether," and the solution is special operating system images for the demo devices. This is something that has been on iOS devices for quite some time; customers can't set passcodes on iOS devices and lock them, and rebooting a Mac returns it to its original state. Back in the old days, yours truly was able to go into Apple Stores and set the default home page to TUAW, but Apple has even figured out a way to keep bloggers from doing that.
Lovejoy's source said that the current OS images on demo devices have a software "kill switch" that disables the devices when they're out of range of the store Wi-Fi network. Apple no longer needs to use Find My iPhone to manually disable devices that are shoplifted.
For devices used for workshops and in-store training, there's a slightly different image that looks and acts closer to what a buyer would see on a newly-purchased device. That kill switch is still in place, however.
There are also HD security cameras in Apple Stores that are hidden very well, so anyone who does manage to walk out with a demo iPhone, iPad or Mac is going to be quite recognizable to the police. The software kill switches should drastically reduce the amount of losses due to shoplifting of demo devices, especially when criminal elements spread the word amongst themselves that they're stealing useless devices.