The island’s not done with you yet
Ok. So, in Season 4 we see a suicidal Michael, in New York City, and low and behold he is incapable of dieing. Then, whatever-his-name-is (the Other who stole Walt in the first place) told Michael “The island’s not done with you yet” and something about not being able to die until the island says so. What the heck does this mean? Why not? What did Michael do that was so important? And a better question, how is it possible that Michael couldn’t die? He even put a loaded gun to his chin, pulled the trigger and it didn’t work.
If the island wanted to keep someone alive, why not Jacob? If the island possesses this power, why not save Jacob if he’s so important? So many people that we believed were important to the island (Locke, Jacob, etc) weren’t protected in this same manner. And we never see this again. The only time the island used this trick was with Michael. Why Michael?
When Mr Friendly was saying the island wont let you die, he was referring to either MiB or Jacob. These two wield the powers of the island and when someone is needed, they heal themn or make sure bad things dont happen to them by protecting them. Someone must have thought it was important that he help his fellow Losties that he left behind by being on that ship.