Well, if you are near the beach, then yes, there will be large concentrations of sand flying through the air. I've seen pictures of what it does and it really will strip the paint and pock mark the metal surface. If you are not near the beach, then you should be aware that the clear coat over your paint is much tougher than saran wrap, so if saran wrap protects it, it wouldn't have scratched the clear coat anyway.
And I would argue that it's worse than nothing because when it blows off in 5 seconds, it's that much more debris flying around.