Sorry to bug all you guys with a haiku-length post, but it just suddenly occured to me what's up with this whole "Flash Sideways" thing they've been doing this season: The purpose of that timeline is to show us what their fates would be if they hadn't crashed, and hence weren't there to save the world.

In other words, if *they* weren't there to prevent it, Smokey McLocke would escape and destroy the world, including, of course, them. The "Sideways" timeline is there to show us *why* all this matters, mattered, why they weren't just getting killed and running around in the woods for no great purpse: the entire fate of the world rests on them keeping Smokey on that island.

Just my theory du jore.