Friend of mine just came back from Tenerife and told me about a QR code scam he saw down there:
Scammers will stick fake QR codes on restaurant tables. QR codes are just website links, so...
1. Link to a fake website that looks like it belongs to the restaurant.
2. Let the customer place a fake order and charge their credit card.
3. Profit!
He said he saw tables with many torn-off QR stickers. The staff would remove the stickers and the scammers would put them back.