Let's just assume for a moment that "Lost has not yet "jumped the shark" (I'd say it hasn't come close yet, but more frustrated viewers would disagree) so, what will be the moment when it does? Damon Lindeloff has said that there'll be a moment around the middle of this season that'll either blow you away, or make you think that it has finally jumped... so, what will that moment be? I'll offer my guess below... but before clicking, you should really try to look at this from Damon's perspective.
He basically said that this one, shocking twist would be the moment that polarizes viewers... either their mind will be blown and start getting "Lost" tattoos, or they will scream in frustration, turn the television off and vow not tow atch anything but "American Idol" from now on.
What could TPTB possibly be planning...? Let's remember, these are the people who have already had a button that could destroy the world, a suburb-like community in the middle of a deserted island, a monster composed of black smoke that can read minds and an electromagnetic "anamoly" that can crash planes and possibly heal people... yet they weren't concerned about Those things. No, but this New thing is the one that worries them.
Somehow, this new "twist" has to be even Further out there than anything they have come up with thus far... so, what could it possibly be? My guess is below.