ZeaLitY, I’ll counter your theory on the origin of the smoke monster with a theory of my own: The woman who raised Jacob and MiB was a smoke monster. She managed to destroy the village where MiB has been living and the people in it all by herself. That seems like an impossible task for one woman alone, unless she had some extraordinary power. As we’ve never seen Jacob exhibit any destructive abilities to stop his brother’s pawns from accomplishing his goals, we must assume that the position of guardian of the source does not include them. So where did they come from?
And how did she know that getting too close to the light was a fate “worse than death?” It’s possible that it was a story passed down from guardian to guardian, but her insistence that Jacob and MiB stay away from it makes it seem as though she has seen it happen to someone in the past or it has happened to her. That’s real fear there. And as it’s a fate worse than death, it would explain why she thanked MiB after provoking him into killing her. Beyond a general tiredness for life (which she never showed), there’s no reason why she would want to die.
But if they were both smoke monsters, why was it so easy to kill her and so difficult to kill MiB? Her death may have only been possible because of her dual nature, unlike when MiB is made into the smoke monster. But how is a smoke monster made?
Here’s where the fun starts. Obviously, there’s a connection to the source. When MiB gets thrown in by Jacob, there’s a lot more gold light in the cave than in later appearances. It’s possible that he saw the light and tried to pull the stone cork out of the pool in an attempt to leave the island; however, since he lacked Desmond’s unique ability to survive electromagnetic events, he was killed before he could get it all the way out. As a result, some of the light escaped and his body was killed in the process. But MiB was always special: He could see the dead. Isn’t it possible this same ability could allow him to latch onto the escaping gold light – or even the red light that we see come up when Desmond successfully pulls out the cork – and use it to bind his spirit to something related to the very essence of the island?
This may be why his mother was so adamant that he not try to leave the island; she feared that his tampering with the island’s energy, even in spots that didn’t hold the stone cork, would transform him into a smoke monster.