I was pondering something that "lostincanada" said, and something they said about the 'prerequisite to kill Jacob' triggered a thought.
We are now left wondering what will be able to kill MiB (smokie), correct? Perhaps this is intertwined with the inability to birth children on the island? What if Smokie is the cause, and he is doing this because he could only die by the hands of someone that was born on the island? If so, this would make Aaron very, VERY important, and maybe the reason he 'claimed' Claire.
I hate to say it, but I really think I am on to something:)