If you ever wanted to use Facebook via TOR you you are no longer forced to use an exit node from TOR. Facebook is now present as a hidden service in TOR at the
URL: https://facebookcorewwwi.onion (only reachable with a TOR-enabled browser of course)
and http://facebookcorewwwi.onion/
They even use a SSL-Cert for the server..
Here is what Roger Dingledine (from the TOR-project) says about the finding of the new URL:
https://lists.torproject.org/pipermail/tor-talk/2014-October/035412.html