"Digital wallets" that let consumers pay with the swipe of a smartphone could make the plastic credit card obsolete. But the technology also could chip away at consumers' privacy—and tempt them to spend more than they otherwise would.
Using a technology known as "near-field communications," or NFC, consumers will be able to buy items simply by passing their phones in front of a sensor at the checkout counter. Though NFC isn't available in many phones yet, a number of companies, including Google Inc., are close to rolling out programs.
By 2014, 70% of U.S. consumers will have smartphones and 52% of those will be NFC-capable, according to estimates by payment consultancy Mercator Advisory Group. Already, app developers, wireless carriers, banks and card companies are racing to shape the potentially lucrative mobile-payments ecosystem.