About a million customers who paid with debit or credit cards were double billed for their Starbucks purchases during the weekend of Memorial Day, according to USA Today. The coffee giant has since corrected the problem, which was due to a “processing snafu.”

This is a good reminder of why you need to keep a watchful eye on debit card activity—look out for errors, whether you check regularly online or review your paper statements. To limit your liability, you need to make reports of fraud in a timely fashion. You have two business days to report a missing debit card to limit your liability to $50, and 60 days to limit your loss to $500. If you found an error on a statement, you have 60 days to report the unauthorized charges or you might be out of luck.

Here are two good reasons why you should keep track of your debit card activity:

1. Rise in Debit Card Fraud
There is a rise in debit card usage, and at the same time, there’s a rise in debit card fraud. According to a recent survey from NICE Systems, there has been a rise in the number of ATM and debit card fraud claims in 2008 from those reported in 2007, and expectations are that there will be another increase this year.

2. Overdraft
It’s good that the Starbucks double billing snafu has been corrected, but what happens to those customers who’ve now been hit with a $34 overdraft fee because they had enough money to cover the purchase, but not double the purchase?
Overdraft occurs when there’s not enough money in your checking account to cover a check, withdrawal, or automatic payment. We’re working on correcting the overdraft problem.