With BTC it will never happen.
FB would more likely create their own coin and sell and accept it.
Thats what I would do if I were greedy

They already using facebooks problem with facebooks in only used in the facebook network, they are clearly losing out if they dont accept bitcoin for there advertising stream.
Yes supposley they are tests going on with it right now that facebook will accept bitcoin for advertising networks. Here is a link of it, not sure if its baloney but hope that answers questions so guys ya better start buying ur bitcoins.
http://bitcoinboard.net/facebook-accepts-bitcoin-on-advertising-platform/Its old news but maybe someone was trying to hype up bitcoin prices?