Lets say it is your birthday. One of your friends goes on my site, selects a gift card from Starbucks and pastes it on your wall. The gift card for Starbucks is worth $0 right now. But then, friends that go on your profile to say happy birthday "like" the giftcard. Lets say 60 friends liked the gift card. At the end of the day you receive a code that you can use in Starbucks as a gift card, valid for $60 pesos.(about 6 dollars)
Really any business could be part of this. Wal-Mart, Starbucks, Dominos, but I would mainly focus on small businesses like independent coffe shops, and bars, which are the ones in need of Facebook prescence and bran awareness.
I tried contacting FB but I havent gotten a response, so I went on this site in the hope of receiving a response by someone who knows about FB policies.