Starbucks continue to innovate like crazy in the social media space. Love what they are doing on Foursquare (bigger post to come on FS soon…). Location-based marketing will be a significant play – for anyone with a location – in the coming year.

Starbucks, a company that already rewards frequent customers with the Barista badge on social gaming app Foursquare — is officially turning on the rewards side of its experimental Foursquare loyalty program with the first-ever nationwide mayor special.

Starting today, mayors of individual Starbucks stores can unlock the Mayor Offer and enjoy a money-saving perk for their frequent store checkins.

The deal offers customers a $1 discount on a Frappucino. The special greets mayors with this message: “As mayor of this store, enjoy $1 off a NEW however-you-want-it Frappuccino blended beverage. Any size, any flavor. Offer valid until 6/28.”

Tristan Walker, who heads up business development at Foursquare (), tells us that the Starbucks special is a one-time mayor deal that runs through June 28, but he’s optimistic that Starbucks will continue to experiment with mayor rewards on an ongoing basis. “Starbucks is particularly innovative as it relates loyalty and social media,” Walker noted, “so we continue to be super excited to explore this intersection with them.”

There are a number of reasons why the Starbucks nationwide mayor reward is significant. It’s a first for both Foursquare and the coffee retailer, and will likely bring mass attention to the marketing possibilities of the location-sharing trend.