By reading the encrypted data off of two cards and testing thousands of potential site codes against both cards until the decoded data displays a predictable interval between the two, he can find the site code and use it to create more card keys with a magnetizing device.

FORBES: Hacker Will Expose Potential Security Flaw In Four Million Hotel Room Keycard Locks

For in-store scenarios either at the register or in the aisle, MasterPass supports the use of NFC, QR codes, tags, mobile devices used at points of sale or traditional plastic cards.

ENGADGET: MasterCard announces MasterPass digital banking service, gives Australia and Canada first dibs

Thieves have been known to troll stores, writing down the redemption codes or registration numbers on cards, then registering the cards and draining them of cash.

FORBES: 10 Things You Should Know Before Buying A Gift Card

Introduced in 2011, the VPP enabled companies can buy a large set of App Store redemption codes that it can distribute to employees, like gift cards, to buy apps.

FORBES: Four Ways Apple Is Evolving Mobile App Management

Hotel de Londres in San Sebastian, Spain, the Signature Hotels in Jeddah and Medina, Saudi Arabia, and HTEL Serviced Apartments in Amsterdam are among the growing number of hotels currently posting QR codes at concierge desks, in lifts and on hotel room information cards to assist guests with tips on where to dine or what to do during their stay.

BBC: Rio de Janeiro brings QR codes to its streets