I think in some cases there should be an option to limit the enabled user to see a file online (photo), to listen to a file (music) and to watch a file (e.g. movie) but the user cannot download the file(s).

As it is all my enabled users can e.g. download the music I share with Pogoplug and share these files with others and I would not even know about it. Apart from the legal issues involved I would like to be sure that my files only go where they should go....