Does your favorite shoe company does have facebook account ? Lets say, Nike, Adidas? Do you follow their fan page? What about a famous convenient store in your place?
Well, this is a bit obvious on why should company have an facebook account. They can reach easily to their customers concerns and product enhancement. They can get comments and reactions via commenting. They can launch easily their product without costing too much unlike the traditional media outlets. That is print ads, TV ads even radio ads. Maybe other than I mentioned was to get their demographics of customers. Kids, Adults, Teens, OSY, Professionals - sure they can come up of a data.
So if this company can pull it off, does on-line people who wants more traffic can do it too? For the fact that they don't have a "name" offline( brand perse ). Here's an idea if I have a site with a market niche on sports ( bastketball to be specific). You post a stories or player highlights on facebook them link them into your site. I can search in facebook someones player, an All-star player I guess. How about Yao Ming. In a all-star balloting he can got a million votes. Do you know how many chinese all over the world? He must have, if not millions, a hundred thousand of fans that I can add up. Let's just say you reach also the number of followers with the same numbers of followers of that players in a certain period of time that would be in a month just adding friends randomly. Then these new friends of yours click your link of posted stories and lead them visiting your site. Again if not millions, hundred thousands visiting your site and how much it can generate earnings. I can't imagine.
Just plain fail.