Smokey mania!

Okay well, whatever "Across the Sea" ends up revealing, I can already tell that I was wrong about the two kids.

BUT, not so much the smoke monster..Okay, so the Man in Black always was a person. But he DID tell Richard Alpert that Jacob not only stole his body, but his humanity as well. I'm still holding onto my theory that the smoke monster was essentially the island itself, or the security system of the island which merged with MIB's spirit when he went down the Holy Waterfall. Also, his body is already dead, so clearly what the MIB wants is not to die, in the normal sense, but to be separated from the smoke monster/security system. If Mother was also so afflicted, then that was why she needed to be killed, to be re-separated from the smoke monster.

By the way, remember back, waaaay back in season 1 when Locke told Jack, "I've looked into the eye of this island, and what I saw, was beautiful!" Go back and look at the cave that Mother showed the twins. It literally looks like an eye! I submit that that was what Locke saw during his first confrontation with the smoke monster: the memory of that encounter MIB had with the Source. Or better, the smoke monster's own view from within that light.