With pump limits, for example, "There is no policy that limits transactions at the pump from MasterCard," says spokesman Tristan Jordan. "The merchants themselves make the decision."
Most credit card companies say that the merchants opt to put the pump limit at exactly the "chargeback" limit -- the highest amount the credit card company will pay a merchant if the transaction turns out to be fraudulent. In other words, they claim merchants cut off customers at the amount the bank will pay if the customer doesn't pay the bill.