The problem with doing this starts with it being against the terms and conditions of every frequent flyer program. I'm not here to defend FFP T&Cs, but the airlines care about this one. They have fraud detection departments that are on the lookout for that sort of thing. Those people are good at what they do and keep getting better. If you buy such a ticket you are likely to be told at check-in that it's no good, and why. (One method they use to tell purchasers from friends and family who were given tickets as legitimate gifts is to ask the traveler questions about the person whose account the miles came from. A friend or family member would know the answers. A stranger who bought an award ticket from an agency wouldn't.) At that point you have a simple choice: pay the last-minute walk-up fare for your flight or stay where you are.