I was reading a post by Mittelman called "The Pawn's Eye View" and the comments, and something clicked in my head that I've been thinking about for a while, so I'll bring it up here. I believe that there are some "BIG" events that cannot be changed, and that will happen, but I believe the ways that they come to be, and the consequences of their occurring, can be affected by individuals and choice. I think this would satisfy both the Whatever Happened Happened and the Future Changed crowd.
For example, Ben was always going to be brought up by the Others, one way or the other, after being saved from near-death ala Smokey. However, maybe the first time, he was running through the jungle and got impaled on a branch. Richard finds him, saves him, and Ben grows into the magnificent bastard we all know and love. However, second time around, Sayid shoots him... but then Kate selflessly gives her blood to keep him alive, and Juliet operates on him, and Sawyer risks blowing his cover by taking him with Kate to the Others. Same thing happens: Ben is saved by Smokey. Now, let's say sometime in the future, Ben is in a situation where he could choose to sacrifice some of the Losties (maybe Kate, Juliet, and Sawyer) to get some desired result in an easier fashion. This result would cause a so-called "BIG" event, one that cannot be stopped from happening. However, what if he somehow gets his memories back, and he's so touched that they risked so much to save him when he was young, that he decides to return the favor? Or even if he doesn't fully remember, perhaps he has some subconscious feeling that he shouldn't just kill these people... and he doesn't understand why, but he makes the choice to save them anyway, obtaining the same result in a different fashion. The BIG event STILL HAPPENS, but the WAY IT HAPPENS changes: Kate, Juliet and Sawyer are alive.
Here's another example. Charlie was ALWAYS going to die, one way or the other. But what if Desmond (and I know this is absurd but just bear with me a moment) decided to fully dedicate the rest of his life to saving Charlie from the various ways he would die? Desmond always got a future-flash with plenty of time to warn and save Charlie, so what if he just kept it up? Theoretically, Charlie could live his whole life (albeit in a weird way) and then still die... OF OLD AGE. Boom, the Universe has its way eventually, and yet because of individual actions (Desmond saving him again and again), it happened in a different fashion.
Now the biggie: the Incident. It was ALWAYS going to happen, but what if the first time around, it happened naturally as a result of the electromagnetic energy release, and the second time around it happened because of the nuke? IT STILL HAPPENS, and yet perhaps the fact that the Losties set off the nuke has subtle ramifications that are only felt later on. What these ramifications may be, we can only wait and see.
I am beginning to feel like the major focus of Season Six is going to be that some BIG event, maybe the BIGGEST OF BIG events, is going to occur. This BIG event will happen no matter what, but with a small bit of change one way or the other, it could either end the world, or save it. The only thing that can change it one way or the other are our Losties. How they have lived their lives, and the choices that they have already made and will yet make, will impact this event to either save or damn us all. Maybe this is why Daniel became so fascinated with individuals as VARIABLES. Perhaps this is why Jacob emphasizes CHOICE so much, even though it would outwardly appear that we are pawns in a larger game, and the future cannot be changed. The Universe will always course-correct so those BIG events that need to happen, will happen... but life still goes on around them, and people may still live or die based on the choices of individuals.