I can't believe I'm just now thinking of this. For when I have to write a check - rent for instance - it just occurred to me that I could purchase a money order using a mileage earning card. A money order costs $0.79. If I write a check for $800, then those miles cost me 1/10 of a cent each. Given that I have to spend the money anyway, I'm only out of pocket the $0.79. It's a no brainer, right? Is there something I'm missing? One then has to ask - what's to stop someone from churning money orders? They're cheap enough, and the turnaround would be pretty quick.