I'm a security guard for a major UK supermarket chain working in a city centre convenience store. Since contactless cards went live we've gone from almost no (detectable) card fraud cases, to the point where the Police are contacting us regularly, wanting CCTV of thieves using stolen contactless cards.
Shame they aren't so proactive when we report known homeless junkie thieves with no prior record of purchasing alcohol suddenly appearing in store to buy relatively expensive spirits with cards not in their name.