Companies customize campaigns by offering different types of “specials” to users, and they can track aggregate statistics throughout the campaign. While RadioShack and others aim to attract new customers, Applebee’s launched a “swarm offer” in an effort to bring in the late-night crowd. Everyone who checks in gets free mozzarella sticks, as long as at least five people in the restaurant check in after 9 p.m.

The real value of Foursquare is likely to become apparent when companies move beyond pilot tests and integrate its data into their broader marketing tools and systems for customer-relationship management. Parker says RadioShack is looking to combine data from Foursquare and other social-media tools, such as Facebook Places, Google Places, and Twitter, into an overall content-management system and customer database.

For companies without physical locations, like content providers or consumer packaged-goods companies, it’s not so simple to analyze the effectiveness of marketing through Foursquare. Companies can try to increase loyalty by creating brand pages where Foursquare followers can see tips for things to do in different cities. For example, the New York Times’ more than 90,000 followers might be advised to try the cereal-milk soft-serve ice cream at New York’s Momofuku Milk Bar. As with Twitter “followers” or Facebook “likes,” companies can monitor their follower count and track how many people have followed up on a certain tip (148 for Milk Bar). But Foursquare’s Friedman says, “We are just beginning to scratch the surface on what that [following] means … and thinking a lot about how to make that data available.”

Carine Carmy is a senior consultant at the strategic advisory firm MarketspaceNext, where she analyzes the implications of emerging media and technology on businesses.