Earthjustice, a non-profit public interest law firm, has blanketed San Francisco BART stations with posters that instruct riders to check in to the "Earthjustice ad" on Foursquare to help the firm raise money to support its wildlife protection initiatives.
The posters take a critical look at environmental issues in the news, such as the BP oil spill in the Gulf of Mexico. That particular poster -- as seen above -- reads, "Use your cell phone to drill the oil industry." For each Earthjustice ad checkin, a company donor with donate $10 to the cause in question -- in this case, "unsafe oil drilling."
The effort is specifically targeted at younger audiences who don't typically respond to messages in advertisements. The hope is that by combining a compelling and relevant message with the Foursquare checkin donation, the younger demographic will be inspired to take an active interest in environmental causes.