Jacob Killed MiB
Think about it. Jacob died AFTER MiB. Jacob was killed by Ben at the end of Season 5. Prior to that, MiB had to have been dead (assuming he was once a man) – hence his ability to shape-shift, steal bodies, etc. I’m betting the farm that both Jacob and MiB were both men, brothers even. If this is the case, MiB died or was killed. I postulate that he was killed – by Jacob.
Why would you want to kill your brother – “Do you know how much I want to kill you?” (MiB; in The Incident). Most likely because he killed you first (I know, go with me on it – it is Lost). I think Jacob killed MiB way back in the day hence the desire for revenge. Since his death he has been able to shape shift, steal bodies, turn into Smokie and all that. How? I don’t know. Point is, if you accept that Jacob killed MiB, then you are granted the insight into MiB’s motivation. Short theory, little evidence, but just enough logic to make it a more than credible assertion. Thoughts?