We are already seeing people offering special deals to the Foursquare "mayor" of their businesses. Today, BART (one of the San Francisco Bay Area's public transit systems) is announcing a partnership with Foursquare to reward users who check in on BART. Foursquare is introducing a special badge for regular riders of BART and offering $25 promotional tickets for the first three months of November to random users who have checked in on BART.
Programs like this are going to be what brings Foursquare into the mainstream. Foursquare already has a very loyal user base, but it still remains relatively small. By offering incentives to use the service, Foursquare will be better able to draw more users. Foursquare has been actively pursuing businesses and encouraging them to offer specials to their users.
Speaking about the announcement of this partnership, co-founder Dennis Crowley said, "We're excited about the potential for Foursquare to influence people's actions and decisions beyond things like entertainment, into broader areas, like taking public transit or getting involved in their communities." This deal with BART is a great step toward expanding Foursquare beyond a leaderboard for bar hopping.