It seems that some companies like Payvment and Tabjuice have had some success getting brands to buy in and use their platforms to sell to fans...but again it just seems like fans are not interested in buying through Facebook. It might just be an undeveloped technology, or its too soon to tell, maybe it will reemerge as something different in the coming years. Also, consumers are probably skeptical about buying through a social network for actual goods, much the same way consumers were a bit reluctant to share their credit card online in the early days of the internet.