How many frequent-flier miles or hotel points have you earned without setting foot on a plane or sleeping in a bed other than your own? To what lengths would you go to beef up your account?

Most of us have credit cards that earn points with at least one of the many loyalty programs available. There also are Web sites that track promotions in various industries on a daily basis. Then there are those deals that were never meant to be deals. About two years ago, American Express Co., the fourth-largest U.S. credit card issuer, began what company officials called a pilot program that allowed customers to use their cards to buy traveler’s checks without the standard $15 fee…