[Elladan and Elrohir]

I don't think it's as simple as "Well, PJ has to cut stuff to make a movie of reasonable length." That's part of it, but he also has to make changes, and even in some cases additions. Because, obviously, you can't directly translate a book to film, and make it work. I used to think you could, but after hearing what Philippa Boyens has had to say, I now think differently.

That's not to say that I think the Aragorn-goes-off-the-cliff addition is great and should have been done the way it was. But I definitely think you can make an argument that this accomplishes some key things in the film. It deepens Eowyn's affection for Aragorn. It empowers Arwen to actually be able to do something significant in the film, which is important because Arwen stands for hope in this movie, and hope is one of its biggest themes. It provides a more dramatic way for Theoden to learn of the coming of the hosts of Isengard. There may be other reasons as well.

Again, I'm not saying I like it or agree with it. I'm just saying that there are reasons within the context of the film, and I can at least partially understand why they inserted it in there.