This move isn't to prevent CC fraud, per se... It's to "protect" the gas station from not getting paid for fraudulent sales. CC issuers have limits on "swipe only" (with no signature) sales that they will still pay to the retailer if the CC use is later challenged or found out to be fraudulent. With the price of gas being what it is now, more and more pump purchases exceed that limit (IIRC, Visa is $50, MC is $75). That limit is waived, or they charge the retailer a lower processing fee, if there is a secondary piece of information that can be provided with the sale that provides some reassurance that the buyer is the cardholder. Usually it is a numeric value associated with the account.
When my wife and I accepted CCs at craft shows, we didn't have a cell phone "swiper". So we used the old fashioned paper slips, wrote down the card and purchaser info and hand punched them into our terminal when we got home. The terminal would ask for either the card holder's house number on their street address or their ZIP code. If we answered "correctly", the processor charged us a lower fee for that sale because it was "safer".... if the number didn't match then they charged us more.
