you take a very great risk - and so does the passenger. Not only do check-in-staff first, mileage programs later (automatically) check if the names on the ticket fit the ff-program name - in these anti-terrorst-fight-days immigration (US immigration in the first place) now have (electronically) access to the passengers files with the incoming airline (showing all these informations like names, age, how you paid for the ticket, your flight patterns by having access to your frequent-flier history, etc. etc.).

Don't do it!