American Express Case Study: Using Prepaid Cards to Target the Travel Market.Presents a case study related to the pre-paid travel card--the American Express TravelFunds Card, conducted by Datamonitor PLC, a premium business information company specializing in industry analysis. Introduction of the TravelFunds card in the U.S. in October 2003 by American Express Co., the global leader in traveler's checks; Focuses on business volume of prepaid travel cards; Strengths of prepaid cards; Security issues as reasons for people to get into using the card, despite the high costs associated with it.