At least several hundred mile-junkies discovered that a free
shipping offer on presidential and Native American $1 coins,
sold at face value by the U.S. Mint, amounted to printing free
frequent-flier miles. Mileage lovers ordered more than $1
million in coins until the Mint started identifying them and
cutting them off.
Coin buyers charged the purchases, sold in boxes of 250 coins, to
a credit card that offers frequent-flier mile awards, then took
the shipments straight to the bank. They then used the coins they
deposited to pay their credit-card bills. Their only cost: the car
trip to make the deposit.