83 million people play FarmVille on Facebook and is not only the main reason users visit the site it also encourages new members. So can FarmVille live without Facebook - very likely and they could start their own gaming group site.
Facebook credits have been introduced a virtual currency that can be used only on the site, and yes, Facebook take 30%!
So you may be fighting the Mafia or growing crops off Facebook in the future unless the two giants can get together and do a deal that suits both...
FaceVille?