I can't stand those ghost bikes and other memorials, they're ridiculous. I feel honestly bad for the people that died, but having these goofy home-made memorials is not the answer, imo. As I always tell my wife, if I get killed while out riding, do NOT put up a ghost bike up in my name.
An interesting story about these memorials: A few years ago we were driving down a highway, and in the middle was a small island of grass. And there, with cars passing on both sides at freeway speeds, was a woman installing a home-made memorial. Next to her was her 1 or 2 y/o little girl walking around on the grass with cars flying by within inches of her, while the (oblivious) mom carefully set up the flowers and cards. There could easily have been the need for a 2nd memorial that day..