I have to say that I have picked up a at least 5 clients in the past 3 weeks from Facebook.
Admittedly- some have been to complete their Facebook Welcome Pages and Business Pages in general- as I said- I think it is a HUGE Marketing Tool.
Of course it may depend on your Niche and the way you run your company.
I found this article very interesting:
Article
Feel free to join my page- and I will do the same
www.facebook.com/dawsondocumentsva
Erin