Prepaid cards are everywhere these days, quickly replacing cash and checks as the fastest way to transfer money. If you're not familiar with them, they function much like checking account debit cards, but do not have the same protections as a bank account. The number of American consumers using this kind of plastic increased to 13 percent in 2011 from 11 percent in 2010, according to an April report from Javelin Strategy & Research, a market research group.