In October of 2009, Bay Area Rapid Transit (BART) partnered with Foursquare to promote public transit use:

Bay Area Rapid Transit has become the first transit agency to partner with the location-based mobile network Foursquare, with the goal of encouraging public transit use. . . .

"A lot of BART riders are already having fun with this game," said Timothy Moore, BART website manager. "We hope this partnership will encourage them to check out different stations and neighborhoods, and will show people who aren't already BART riders some of the great things to do that are easy to get to on transit."

The agency released the results of a consumer survey (1/10 - 3/10, n=446) conducted earlier this year. It appears to be creating more "fun" and engagement around public transportation for the riders using Foursquare:

• 23% percent of respondents . . . said they had earned a BART frequent rider badge; 7% said they had become "mayor" of a BART station.
• 38% of respondents said "it's more fun to ride BART" as a Foursquare user
• 17% said they had used Foursquare to connect with friends on the train or at the station
• 43% had used Foursquare to recommend a destination near BART in the past three months
• 19% had used BART because of a Foursquare recommendation

Finally:

Nearly a third of respondents said they typically ride BART five days per week; a third also said they check in regularly on Foursquare at BART stations. Fourteen percent said they're riding BART more often because of their interaction with Foursquare.

So the experiment and unlikely partnership appears to be a success. With more riders, hopefully BART can hold off the relentless fare increases.