With Facebook, there is usually a use for it with any business. It just depends on the audience your business attracts and how they want to be engaged.
You may say “well, why does Coke have a Facebook Fan Page?” Their use of a Facebook Fan page is one of the best. Just look at the pictures that their users submit. They submit pictures of people and coca cola.
Joe uploads a picture of his wife drinking a coke, through Joe’s stream, his friends can see a picture of his wife drinking coke. Joe tags his wife in the photo, his wife’s friends can now see that she has been tagged in a photo of her drinking coke. One of Joe’s friends, likes or comments the photo, all of Joe’s friend’s friends, can now see that he commented on someone drinking a coke.
See the flow! The brand gets out there whether you notice it or not. I bet the next time you wanted something to drink, that you went out and bought a coke.