The only way out by Semola

Apologies to anyone who already said this.

Flash sideways = REAL and ONLY REALITY (ROR)

Flashbacks = a kind of reality built by the island, based on losties fears, desire and memories, all experienced by a sort of bad twin of yourself.

Jacob did the rules on island bubble, so when you get in, you feel it like real but it's not real. All the time spent on the island, individually for each character, takes the time of a blink of an eye in ROR.
There is no way out from the island but death. Once you die all the memories of what you experienced on the island merge in your subconscious in the ROR.

Why or how you enter the island is quiet unknown at this time, but I think this is the only way TPTB have to get everithing tied up.

On the island time is a relative term, because once you get in you could spend centuries on it (richard) but when you die you go back exactly at the moment you left ROR for the island.

Go to see LAX episode, the very first scene, and look closely at Jack's face. He looks like is feeling something weird but just don't know what it is. He just got a lot of informations about himself and other people but is not fully aware of it yet.

So in conclusion:
Jack has issues with his son, and once he got on the island he found himself in a situation where he can feel on his skin what is like having a father who don't understand you.
Locke could not let go the fact he's responsible of A.Cooper conditions, so once on the island he's facing a cruel father to see if he's able to get over it.
Sawyer is always been a cop seeking revenge, and once in the island he became the man he is after in ROR.
...and so on.

Maybe MIB knows it and when he says he want to go home, it's just he found a way to die, and go back to the moment Claudia went on the island. Don't forget Claudia was killed after a few hours spent on island, so maybe for her, waking up in ROR, was just having a bad dream. But his son (sons) is not born yet and that is when and where MIB is trying to go back.

When Ben says to Locke about the magic box, I think he was saying to us that once you're inside this bubble everything you fear or desire simply appear because that is the cause of your own suffering and you're here to face it.

So the great things TPTB are giving us are that everyone of us could have been on the island already, we simply just don't remember it, but every deja-vu or dream or weird sensation we have in particular moments, maybe are just the memories of real experiences we lived on the island that are trying to get out from our consciousness.

In conclusion there's still much to say, for example:
is this a casual phenomena or there someone aware of who is bringing, I don't know how, people on the island?
Is this someone trying to exploit it for his own good?
Is there someone else who is fighting against him to prevent this from happening?
I don't know, but I think I'm onto something here.

I'm sorry for bad english, I did my best.