I came across this article from PBS and Frontline that did an entire series about the Secret History of the Credit Card.  I will tell you, this will challenge even the most confident consumers when it comes to being fiscally sound.  Watch these online videos and learn some hard facts such as:

Did you know that you can have your interest rate changed based on your behavior with a completely unrelated creditor?  Even if you have never been late with your MasterCard creditor, but say, 3 years ago were 60 days late for a payment on your car, your MasterCard holder could decide at anytime to change your current interest rate (regardless of the intro terms) to a much higher rate. 

This could change your attitude the next time you pull out the plastic.