I stole this theory from two of my friends. But it is great. Jacob's cabin was never Jacob's cabin. The Otherman was imprisoned in the cabin by Jacob. Christian Shepard was the otherman talking to Lock, playing him for the sucker he is, was, and always will be.
That is why Ilana freaked out when they saw the Ash line was broken, and the Cabin empty. They were going there to show Otherman/Locke 2.0 that they had Locke 1.0's body and the game was up.
All these manifestation, Yemi, Ben's mom, Claire, Christian Shepard, they are all done by the the other guy, trying to break from his prison and ultimately knock off Jacob. That is the significance of properly burying someone on the island. If they are not buried, Otherman can take their spirit, and use it to trick or lure someone.