The average overdraft fee last year was $27.40, according to Bankrate.com. In annual percentage terms, that amounts to a median interest rate of more than 20,000 percent on overdrawn debit-card purchases, according to the study, which looked at the overdraft fees that banks and credit unions charge and analyzed 8,527 overdraft transactions…
Industry experts say overdraft fees are the biggest single source of fee income in retail banking. U.S. consumers pay $10.3 billion annually in overdraft charges, about $7.3 billion of which comes from “chronic borrowers living on the margins,” according to the report. Further, these borrowers are more likely than other bank customers to be single, non-white and renters rather than homeowners.

http://www.newsobserver.com/666/story/536351.html
More:
Debit-Card-Danger-report.pdf