Bad idea. The one big reason gnutella is so successful and has the
widest variety of files is because it welcomes all people even if they don't
have files to share. Attempting to force people to share something, anything,
always results in either them sharing millions of junk files from a Windows or
program folder or they end up sharing a small collection of what everyone else
already has shared.

The amount of people on the network with nothing to share has steadily
dropped over the years to a stable level of about 12%, and that's perfectly
healthy for the network on the whole. Any selfish attempt to force the
percentage lower will just drive people away, doing more harm than good.

If you want a totalitarian network which ends up forcing nearly everyone into
copyright infringement then go to something like DC or one of those private
torrent trackers that think they're so kewl and leave the rest of us to share
in perfect freedom.