If you muck about in the library in finder, you will cause iPhoto to not work! Let iPhoto organize things for you, you do your own organization (via albums, smart albums, folders, etc.) from within the app itself. Using keywords, you can find any photo instantly. Give it a try. But DO stay out of the finder! You don't want to corrupt or lose your photos, or access to them, and changing things in the finder will result in just that!