Okay, so remember, Sam stood and watched Dean get turned, but he actually DID know there was a cure.
He also trusted Dean well enough to know he wouldn't feed.
Sam has a plan, and it has to do with ferretting out the Alphas. (this alpha storyline is a little too Buffy for me, but whatevs.)
Did you notice how many times he asked Dean what he saw?
And so, now, what do we think brought Sam back??? What is the source behind the Alphas -- the Alpha OF Alphas???
Could it be the Alpha/Omega? And would that be "God" or some other Prime Mover?? It would be really neat if the Angels' God is no more the ur-source than the pagan gods we've met here and there. ... And that Sam is now working as an Agent of whatever brought him, something intent on restoring the balance that the Angels' and Demons' apocalypse upset.
Thoughts?