I personally think Rose and/or Bernard is somehow behind everything. They just seem 'too nice' to be brought to this island where everyone else has a 'mean' past (mean meaning bad, killer, deadly, etc).
one of my friends said something funny. their theory of 'Lost' is that it is Hurley's dream. That he is still in the mental hospital and dreams up all of this, hence why the numbers are everywhere and everyone that is on the island is actually in the mental hospital. Would be a funny ending but also a shitty one.