We've already seen that now with Locke. He wasn't destined to be the leader of the Others or fated to be. He went back in time and told Richard who he was and when he was born, etc... so he created his own "destiny" to be the leader of the Others, which means it wasn't destiny at all.
I have to say that really bugs me because of the predestined paradox that situation creates. The time traveling element right now is creating a lot of situations for such paradoxes and that has me worried. I'm willing to trust the writers to the end, but it is the one thing going on the show right now that concerns me.
Anyone find it funny that John Terry's character (Christian Shephard) was dead before the pilot episode yet they've done more with his character -- pre and post death -- than Boone, Shannon, Libby, Charlotte and others combined?
Yeah, I've noticed that for awhile now. I love it.