Americans love their debit cards, with use surging so much over the last decade that consumers are swiping them at the register almost as often as credit cards.

It's not hard to understand why. Both credit and debit cards offer the convenience of not having to carry a wad of cash, but debit cards -- also called check cards -- help consumers control spending, too. The cards take money directly from customers' checking accounts, typically preventing them from running up big bills.

But along with the debit cards' growing popularity come some pitfalls that experts say consumers should know.

For one, complicated funds availability rules and other bank policies are making it easier for consumers to overdraw their accounts and get hit with fees.

For another, consumer protections generally are not as strong for debit cards as they are with credit cards. Unlike debit cards, customers using credit cards have charge-back rights.

If, for instance, a credit card customer orders merchandise and receives the wrong order or inferior goods, the customer can withhold payment while the credit card company mediates the dispute with the merchant. That's not possible with a debit card.

In addition, federal rules protecting consumers against fraud are weaker for debit cards, an issue of growing concern as cyber thieves appear to be favoring debit cards over credit cards because of the ease with which they can obtain cash.

With credit cards, liability for unauthorized transactions is limited to $50. But since most card issuers have zero liability policies, customers typically aren't on the hook for anything.

With debit cards, liability is limited to $50 only if customers notify their financial institution within two business days after realizing their card has been lost or stolen. After that, liability is capped at $500 if suspicious activity is reported within 60 days of receiving a statement. Beyond 60 days, the sky's the limit.

"Liability under federal law could start at $50 and go up to as much as the entire account plus an overdraft line of credit if [the consumer] didn't catch the fraud and report it," said Gerri Detweiler, author and consumer debt adviser.

The good news is financial institutions generally are more lenient than the regulations require, said Paul Kaboth, assistant vice president with the supervision and regulation department at the Federal Reserve.

Most financial institutions cover their customers' entire loss, "unless they are really concerned that the consumer is not acting in good faith," he said.

In addition, Visa and MasterCard

have zero liability policies on debit card purchases processed through their networks. Those types of transactions, using cards with the Visa or MasterCard logo, require authorization with a signature instead of a personal identification number.

Despite those protections, it's good practice to review bank statements carefully and report problems immediately, the Fed's Mr. Kaboth said.

Banks are allowed up to 10 days to research disputed debit card transactions before making any credits. That can be a long time to be without the money. (Banks actually can take up to 45 days to investigate, but must credit the account after 10 days while they finish the investigation.)

Debit card fraud is something more Americans could be confronting.

Experts say cyberthieves increasingly are focusing on debit cards instead of credit cards because stealing cash from an account is more attractive than making fraudulent purchases.

Another problem people face with debit cards is losing track of their balance and overdrawing their accounts. Even customers who check their balances frequently can get caught, since the tally could include deposits or outstanding checks that haven't cleared.

"If you are believing the balance on the 800 number or your online bank statement you can easily overdraw your bank account," said Jean Ann Fox, director of consumer protection for the Consumer Federation of America.

A growing number of banks also are automatically enrolling customers in so-called courtesy overdraft protection programs that make it even easier to slip up.

Under the programs, banks allow customers to overdraw their accounts at the register -- for a fee, of course.

Fees typically range from $30 to $35 per item. That means a $2 bottle of Pepsi that pushes someone into the red can end up costing $32 or more with bank fees.

"For years, people said if you can't handle a credit card, use a debit card because you can't get into debt problems. That is no longer true," Ms. Fox said.

Ms. Fox said she uses debit cards, but "cautiously."

She keeps track of all her purchases, just like she does when she writes a check, and keeps a running balance.

And she only uses a debit card at local retailers where she can "look somebody in the face," just in case she encounters a billing or other problem.

"I never use a debit card online or to order something over the phone," she said. "If I'm dealing with someone I don't know, I use a credit card."