Thanks, HansTWN. For the sake of discussion, here is my proposal for "social DRM":
Media files are sold (not licensed) to buyers. When a buyer downloads a media file, her/his own copy of it includes embedded metadata that allow the seller to identify who bought it, and when. Buyers can do whatever they want with their files, such as giving a copy of them to their family; on the other side, they have a responsibility in the consequences of what they do.
If a media file gets illegally distributed (e.g., it is published on a torrent site) the original buyer of that file is considered responsible of illegal distribution along with the actual distributor, unless one or both of the following conditions apply:
1) on day X, before the illegal distribution, the owner of the file notified the police of a theft of property or data which included media files, and the illegally distributed file was purchased before day X;
2) the file owner is able to identify the physical person who actually distributed the file, and this person confirms to have done that, taking all the responsibility of the act.