Here's a theory I read at TV Fanatic that I really like...
Eloise told Desmond that he had the life he always wanted, specifically: the admiration of Charles Widmore. Desmond should accept it, be happy and stop searching. Why? He wasn't ready for the truth yet.My only problem here is the 'love' has never been one of the big LOST themes (in my opinion).... Ah well.
What is that truth? This is my theory: it's related to a deal those on the island made with FakeLocke. He's been manipulating people throughout the season, inching closer and closer to his goal of freedom. His main strategy for conspiring to leave the island? Convince the castaways that he can make their dreams come true.
You want Nadia to be alive, Sayid? No problem! Wanna see Jin again, Sun? I can do that! Care to be a mother to Aaron, Claire? Follow me!
In each instance, FakeLocke is trying to get people to take his side over Jacob. And what's been the theme that both Widmore and Jacob (the two men opposing the Man in Black) have tried to hammer home to anyone that will listen? If FakeLocke succeeds, the world that we know will end. There's no way of understanding exactly what this means, or how it will take place, or a million other questions hanging over Lost.
But Eloise's speech, and Daniel's subsequent hypothesis about his own past, lends credence to the idea that FakeLocke promised everyone their very own heaven in exchange for his freedom, but you know what they say: be careful what you wish for.
Because something is missing in this Man-in-Black-created universe. It's something Charlie saw in his near-death experience: love.
It sounds cheesy, but think about it: Sayid isn't actually with Nadia in his Sideways world. Jack is divorced, Sawyer ruined things with Charlotte, Desmond is completely alone. These individuals may have been granted their wishes by FakeLocke, but the result was far from the ideal life they had envisioned once they conquered their past demons.
What does all this mean? Who knows. But Daniel made it clear that this Sideways world is not the life they are "supposed" to be living ("What if this all this wasn't supposed to be our life? What if we had some other life, and for some reason we changed things?") .
Something went wrong, and all signs point to that something having a lot to do with Jacob's nemesis. The Man in Black may have told Richard, in "Ab Aeterno," that he was NOT the Devil - but it certainly seems like our castaways have made a deal with someone evil that has resulted in a major, loveless shift to their universe.
Could that be FakeLocke's plan? The danger of releasing that cork? He may not literally destroy the world, but he may remove the concept of true love from it.