clipped from: www.tbo.com   
One of the biggest selling points for debit cards has been that you couldn't spend more than you had in your bank account, making them a good alternative to racking up debt on a credit card.
But, as many users have discovered, the debit card carries the same problem as its credit card cousin: You can spend over your limit.

The practice of approving a check or debit transaction when the account has insufficient funds is an intentional effort to drive up revenue, according to a new study by the Center for Responsible Lending, a nonprofit, nonpartisan research and policy organization.

"Banks should protect customers' funds, not plunder them with high fees and harmful practices," said Eric Halperin, director of the center's Washington office.

This year, the center published a report that found that debit card purchases at point of sale terminals and withdrawals at ATMs triggered 46 percent of overdrafts. The rate for paper checks was just 27 percent of overdrafts.