Buying things online is dicier when you pay by debit card, where money is directly taken out of your checking account, than with a credit card, where you can carry debt from month to month. Here’s why it matters: If you shop by credit card and your mail-order merchandise doesn't show up or is shoddy, the law says you can dispute the charge (without paying it) while your card company looks into the situation. But if you pay by debit card, you're on your own. Your bank isn't required to help resolve your shopping problem. And your money? It’s already been zapped out of your account.
Protect yourself: Use debit cards mostly for purchases at stores you know and trust. Opt for credit cards online and when buying big-ticket items like electronics — just in case anything goes wrong.

Risk: Overdraft Fees

Once upon a time, your debit card would be declined if you didn’t have money in your account to cover a purchase. These days, banks knowingly let you overdraw by offering "courtesy overdraft loans." But there's nothing courteous about them, says Leslie Parrish, senior researcher for the nonprofit Center for Responsible Lending. According to the center’s research, banks now charge an average of $34 per overdraft item. You could easily rack up several charges in just one day.
Protect yourself: Sign up at your bank for real overdraft protection. Link your debit card to a savings or other account so funds are automatically transferred if you accidentally spend more than you have in your checking account. Another option: Ask your financial institution to deny debit transactions that take your balance into the red zone.

Risk: Electronic Fraud

Thieves are now armed with handheld card skimmers that copy your debit or credit card information and allow them to make duplicates of your cards. "If crooks copy your debit card, they can clean out your bank account before you even know anything has happened," warns consumer advocate and radio talk-show host Clark Howard.
Protect yourself: Avoid using debit cards in the riskiest situations — where waiters or gas-station attendants carry your card to a cashier, out of your sight.

Risk: Surprise Holds

Did you know that hotels and gas stations are allowed to temporarily freeze funds in your checking account when you pay by debit? This is to ensure they’ll get paid — before you pump that gas or open the minibar. These holds typically disappear within a couple of days. However, if you maintain a low checking-account balance, a $50 gas hold could cause you to overdraft and get hit with expensive fees.
Protect yourself: Use a credit card to secure hotel rooms; pay cash or by credit card at gas stations. If you must use your debit card for gas, type in your PIN rather than signing for the transaction. Using your PIN eliminates
the hold.