Those of you with card issues; are your cards RFID chipped? the kind you can swipe over the reader without actually pushing the card into the slot on the reader? if so people can build scanners that, whilst operating only over the short range of the card-reader systems that are meant to read the cards for processing payment, and nab the details enough to defraud.
They sell expensive scan-proof wallets but really all they are is a wallet with a faraday cage built in. All you need is to line your own wallet with wire mesh of a fine gauge, that will block the signals and render your card unreadable to the thieving little shitbags whilst in the wallet. Aluminium foil even should work, just make sure the liner is thoroughly enclosing the card(s). Wire mesh would be more durable though, and you could make a little catch to have it snap together with those push-fit buttons and a little extra length of mesh.