Starbucks has been using the hip new Square readers to great acclaim, and will now begin to sell the little squares in stores. Before swiping your credit card, however, there are some safety issues that you need to be aware of.

Walking into a Starbucks and swiping your card will present little problems. You can also be sure that the baristas behind the counter are using Squares that Starbucks fully stands behind.

However, what happens if you meet a vendor on the street, and they offer you payment options by swiping your card on their phone? This is where it gets a little trickier. As these Squares proliferate and become ubiquitous throughout your city, there can be potential security holes.

Square rival VeriFone brought up security concerns in 2011, according to TechCrunch. In an open letter, VeriFone CEO Doug Bergeron mentioned the potential for unscrupulous individuals to use the squares for "skimming" - or taking customers' credit information without their knowledge. As they process the transaction, they also take the card information, and use it later to go on a shopping spree.

 "Consumers who hand over their plastic to merchants using Square devices are unwittingly putting themselves in danger," Bergeron wrote.

Square's CEO Jack Dorsey protested, but followed up by embracing Visa guidelines for safety improvement. These included encrypting information that is read by the card.

Unfortunately, few security steps could prevent a con-man from creating a square-like card in order to swipe information from your card. The best way is to be careful who you hand your card over to, and stick with well-known merchants. But this defeats the purpose of Square, which is to allow small merchants to take credit cards (like Dorsey's business partner Jim McKelvey, who originally inspired the idea by his frustration at not being able to take payments as a small business).

Still, when all else fails, it is assumed that your credit card company will have your back for fraudulent transactions. But the best way to avoid the hassle, and to maintain peace of mind, is to stick with merchants that you know and trust.