i have bought many dvds and games and almost every single one has come loose in the case and has been rattling around inside the box which as im sure you're  aware scratches the disc and potentialy effects the film or game,

to save the hassle of sending some one a disc and it getting scratched in transit, put some buble wrap or something similar IN the box to stop the disc becoming loose or if your buying, request that the seller does this so you get a working disc and the transaction ends with positive feedback.