I seem to recall a somewhat low-level scandal where the Treasury was selling newly minted dollar coins at face value with perhaps free shipping to purchasers using credit cards. The coins reportedly never made it out of banks as people were buying them on credit cards to earn credit card points, stashing them in the bank and then paying the credit card bill with the coins each month (thereby avoiding paying any interest). Million upon million of credit card points were reportedly "earned" in this manner. It did cause the Treasury to change their policy I understand.