I wish I knew about this.
You could buy dollar coins directly from the US mint (supposedly this was to help get them into circulation), but there was a huge flaw in the plan.
They charged no fees on the purchases, and you could pay by credit card.
So you could earn unlimited airline miles by just buying dollars with dollars.
And that's what this guy did: http://www.dailyfinance.com/2013/02/...ne-miles-free/
The funniest thing was the fact that he didn't have unlimited funds, but rather just kept cycling the dollar coins back into the bank to pay off the previous purchases.
He racked up 4 million miles that way, buying $4 million worth of dollar coins.
I estimate the government forked over about $70,000 worth of credit card fees (and some shipping fees, as well) to enable this guy's mileage purchases.