I don't get the point, TOR is meant to conceal your identity, using TOR on Facebook projects a terrible understanding of how it works
E.g. you don't want your ISP to know you're visiting Facebook.
After all, TOR gives you flexibility in privacy, it's up to you how to use it.
Why wouldn't you want them knowing your using Facebook though? I don't understand how that benefits anyone. Most isp allow facebook.