Many merchants are using Facebook as a media to keep contact with their customers. They will run Facebook Fanpage and post updates on product information or company news. Some will be even smarter to use Facebook App in their Fanpage for running marketing campaign.
Trappist Dairy is one of the smart players. We helped Trappist Dairy to build a Facebook App in their Fanpage to promote their flagship dairy products. The Facebook App runs on both desktop and mobile. The three customers with largest spending on their products will receive electric appliance cash coupons. It is a great campaign and customers cannot stop sharing this news to their Facebook friends.