PDF from an Austrian lab reporting on cloning NFC cards a heavy read but basically the message is that the "issuer" ie the company that puts the Logo on the card (Not Mastercard or Visa) have choices that can compromise the level of security. Choices that might reflect the cost of making the card that you don't see. A clone of your card might be possible to be made which would work until you used your card again, simple checks for discrepancies are not always made by the "issuer".

I haven't found a report on how easy it is to rub up against you, the scanner would require batteries but embedded in a wall at pocket height? They only have to get within 4cm of your wallet or purse.

And just in case - be careful leaning over the bar whilst drunk too.

Years ago I bought petrol and one packet of crisps, the ticket listed 3 items. When I queried it the guy said he must have picked up his can of Coke and inadvertently passed it past the scanner. Yea, once inadvertently. Then every time people bought several items thereafter! I nearly shopped him and curiously the filling station changed owners a year later.

I think the credit card companies hope that a pattern emerges and there is a short wait for payment to the alleged vendor. But human nature .............................