Use both of them, they both have a purpose. Facebook is more for fun, like a hobby. LinkedIn is serious, like business.
i like facebook too. it also can help my Business. this is my company page :facebook.com/fiberstorecom
I haven't used my Linkedin to the best of its capabilities, I'm pretty sure I'm missing out on how to fully utilize it. (How do you guys use your linkedin?) It's definitely more serious in tone. FB on the other hand, is more casual, open, literally.
Recent surveys I've seen suggest Linkedin is best for business and this is the site where I have intended to focus my own efforts. However, I see the benefits of facebook for leisure businesses such as pubs, clubs, restaurants etc as they fit well in to the social chat on the site.