There are certain things that movie trailers need to stop doing [Cracked Article], and I think the thing that's the worst is giving the whole movie away. As the linked article points out, the trailer for cast away includes a scene showing
1) The plane crash
2) The things he accomplishes on the island
3) Someone on the rescue plaen later saying "You've been lost for four years"
4) The reunion with the woman he left
5) The last shot of the entire move
Given this trailer you would think that this movie is about what happens when you're gone for four years and then how you deal with everything that has changed. If that's what you were there for, you'd be sitting there in your seat saying "Alright! Here we go! Here comes the conflict I've been waiting for!" and instead, here would come the credits.