The prepaid debit card market is becoming more mainstream, giving customers a wider variety of options and offering more cards that resemble checking accounts. Less regulation, however, means that consumers need to be more careful about their choices. In its annual survey, Bankrate.com looked at the details of the 24 biggest prepaid cards by market share. The types and amounts of fees connected to prepaid cards can vary widely, but there are four fees that consumers should avoid at all costs. The first is a purchase or activation fee, which 10 out of 24 cards have -- although some are free if purchased online rather than in a brick-and-mortar store. The second is a point-of-sale fee, paid whenever the card is used to make a purchase. The third fee is the customer service fee, and the fourth is an inactivity or dormancy fee. American Express' Bluebird, PNC's SmartAccess, and Chase's Liquid cards are examples of prepaid cards that do not carry exorbitant fees. However, many experts say that conventional checking accounts are a better option than prepaid cards for most consumers.