Airlines use sophisticated technology to track unusual account activity, such as booking flights for unrelated third parties from different locations. If caught, the consequences are severe:

: Once a broker buys your miles, they typically use your account to book a "reward flight" for a third party who has paid them for a cheap ticket. The Risks of Selling

: You may be banned from future participation in the airline's loyalty program. Safer Alternatives to Selling

: The traveler using the miles may have their ticket cancelled at the airport, leaving them stranded and potentially leading to legal disputes with you.