Still think Foursquare is just a silly fad for wired extroverts with too much time on their hands? Starbucks is one marketer who sees it differently, eyeing serious sales potential from the location-based social gaming app, announcing this week it will create a U.S.-wide loyalty program for the mayors of Foursquare.

Perhaps that paragraph above needs a further translation (Foursquare die-hards can skip to the next paragraph). Here’s how it goes: Foursquare users check in to favorite shops, cafes, stores, etc and alert their followers where they are using a special app or via text message. The more times you check in at, say, a favorite Starbucks, via the location-based service the higher your status. The one who checks in most to a specific location earns “mayor” status. Got it?

Foursquare and rival Gowalla take marketing loyalty programs to the next level, by introducing an element of gamesmanship plus the ability to share your current status with your Facebook friends or Twitter followers. Or at least that’s the way Starbucks sees it, deciding to reward Starbucks mayors with a $1 discount on a Frappucino whenever they reach that status at any of the chain’s locations across the United States, Mashable reports.

Already, observers are expecting a location-based land rush from retailers and fast-food chains keen to boost foot traffic and learn a bit more about consumer’s shopping habits the moment they walk into the shop. McDonald’s is believed to be planning a similar rewards program, using Facebook, not Foursquare, as the social networking partner.

And what of the leading loyalty card players like Nectar Card? Judging by its anemic Facebook presence, don’t expect much.

Editor’s Note: Want to learn more about social media best practice? Join our LinkedIn Group and enjoy a great discount on attending the Social Media Conference, June 22.