ARBITRAGE: Airmile hackers use mileage credit-cards to buy $1 coins that they use to pay the CC bills. “Airmile hackers figured out that they could buy dollar coins (free shipping!) from the US Mint, using credit cards that gave them airmiles for purchases. Then they took the dollar coins straight to the bank and deposited them, paying off the credit card bills before any interest was incurred. The only cost was gas for the bank-runs.” Never underestimate humans’ ability to game the system . . . .