Here is an interesting theory. Christian tells Locke that to protect the island he needs to move the island ("Cabin Fever"). Assuming this is possible (through the use of some kind of fourth dimension hoop-la), could it be that the island is actually moved to Los Angeles, where it is hidden by all the other matter and people there? This could explain why Hurley suggests to Jack in "Something Nice Back Home" that they never left the island, or more appropriately, the island never left them. This could also explain the reflected city buildings in the Lost logo.

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