Companies like Visa and MasterCard, which maintain networks of financial institutions lending the money and collecting fees every time a card is used, have become spectacularly wealthy through this easy access to credit. Visa's recent initial public offering was the largest in U.S. history, while MasterCard's stock has soared nearly 500 percent since it went public two years ago, their markets overseas growing like wildfire.

But while most cardholders pay off their debt, there remains a very dark side to the credit card, "a deceptively simple device that has the capability of destroying you," says Adam Levin, co-founder of San Francisco-based credit.com.

Critical of the card issuers' heavy fees and aggressive marketing tactics, especially toward finance-naive student and low-income communities, Levin says "people have been bludgeoned" by credit card offers, often going to consumers already struggling with debt. "It's like taking a vampire and putting him in the middle of a blood bank."

One study showed that about 70 percent of students at four-year colleges had at least one credit card, with average balances of more than $2,000. Former San Jose State University student Cynthia Uribe was one of those who succumbed to the on-campus sales pitch.

"I figured I could use it just for emergencies," says Uribe, now 24 and doing clerical work at a local hospital. "But I got more of them, from Best Buy and Macy's and MasterCard. And by the second year, I was using them for fun and pleasure. And making the minimum payment was so much easier than paying the whole thing."