This was said to be the main point of the new chip and pin credit and debit cards. Remember the bad old days of paper transactions, when staff at businesses where you had used a credit card could salvage the carbons from the bin and copy your signature? We've moved on a long way from there. All they have to do now is go into the till history, copy your credit card number and pin, and spend, spend, spend.
The Devil's Kitchen has the details:
Up to 40 minutes after any Chip & PIN card transaction, the retailer may access your confidential details [this includes your card number and your PIN number] and submit any number of further transactions without your presence or consent. This is perfectly legal practice. The onus is then on the customer to challenge these subsequent transactions with their bank, once the customer actually becomes aware of them.
Personally, I just can't wait for I.D. cards to be introduced.