Ok, last night's show totally confused me. As far as I can tell, the only thing we learned last night was who Adam and Eve are, and we now know for sure that Jacob and MIB are brothers. Can somebody help me understand something?
So it looks like Smokey was "living" in that cave where the light was, right? Now, the "mother" told Jacob and his brother (I can't believe they STILL haven't told us MIB's name

) that they can never kill each other. So when Jacob shoved MIB into the light cave, MIB was still alive. Since Jacob found MIB's body and put it in the cave with his "mother" to be Adam and Eve, I assume that Smokey is the one who killed MIB. Right? And then Smokey took MIB's form until he had some other dead bodies (Christian, Locke) that he could inhabit.
BUT.....the end of last season when Jacob and MIB are sitting on the beach and MIB says how much he wants to kill Jacob and how he'll find a loophole. That loophole was MIB/Smokey taking over Locke's body and convincing Ben to kill Jacob.
Well, if MIB had already died, why couldn't Smokey (in MIB's body) kill Jacob? Even if being in MIB's body/form was what prevented Smokey from killing Jacob, why couldn't he do it while he was in Locke's form? Why did he need to get Ben to do it?
Is there something that we don't know about that prevents
Smokey from killing Jacob, no matter what form he's in? And Smokey can't kill the candidates either. So Jack is right - they don't have to be afraid of Smokey because he can't hurt them.