Well, here come the Dark Nets: "The RetroShare network allows people to create a private and encrypted file-sharing network. Users add friends by exchanging PGP certificates with people they trust. All the communication is encrypted using OpenSSL and files that are downloaded from strangers always go through a trusted friend.

In other words, it’s a true Darknet and virtually impossible to monitor by outsiders. http://retroshare.sourceforge.net/