Why Legolas?

There's been a question nagging me ever since I saw the Fellowship a few years back for the first time. During the "Mirror of Galadriel" scene, Frodo looks in the water and sees (in order) Legolas, Merry and Pippin, Sam, and then the (possible) Scouring of the Shire. Now, I get why they're all depressed (obviously indicative of Frodo's potential failure and Sauron's success), but here's what bothers me: why Legolas? If I remember right, he had no purpose in the Scouring in the book, so why should he be shown in a scene about the Scouring?

To further add to this question is the lack of change in the Special Edition. Before buying it, I thought they would add shots of the others looking all glum, or at least give some reason for Legolas being there, but that was not to be.

So please, someone give me a good answer: why Legolas?