The short version: Savvy consumers notice that the U.S. Mint is offering free shipping on presidential and Native American $1 coins, sold at face value. They buy truckloads of these coins using their credit cards, racking up frequent-flier miles. Then, because what they bought can be cashed in anywhere for exactly what they paid, they use the coins to pay off the cards.

Net cost: the time they spend taking the coins to the bank.

Net profit: hundreds of thousands of flier miles and the free trips that come with them, not to mention perks like lifetime upgrade privileges.

As Kottke pointed out, makes the guy who bought all that pudding look like a sucker.