1. Jacob came to Hurley as a child and gave him the gift to be able to see dead people. He's not insane, he was made that way. *Jacob to Hurley in the back of the cab: "I've got some news for you, you're not crazy"*. Jacob made him that way knowing one day he would die and need to talk through Hurley.
2. Candidates cannot die (except specially) on the island or off and cannot age once on the island. If they age on the island, what's the point in making them a candidate..they'd eventually just die of age. Candidates can also die but only by: 1. the hand of man or 2. a natural disaster caused by the hand of man.
Perhaps if Locke had stepped off the table when he was hanging himself, the rope would just break, since he can't kill himself. Michael couldn't kill himself until he was "redeemed" (or as UnLocke calls it, getting "crossed off the list". When the chopper crashed in the water everyone was fine, except for Desmond, who may have been "crossed off the list" too. This is why when Jack lit the dynamite it didn't work because he would be killing himself.
Charlie died as a result of a natural disaster by the hand of man (Patchy <----best nickname ever). Locke was killed by Ben (hand of man). UnLocke had to get Ben to kill Jacob (hand of man)
If this stays true, then perhaps this is the reason UnLocke needs his followers. Since he can't kill candidates, he needs others to do so.
What do you guys think?