One-to-one, private sharing has been a staple of the file-trading scene since the late-90s.
Users can share enormous files through apps like AOL Instant Messenger (AIM), or even email and shared virtual hosting accounts. A close cousin is the limited-access LAN, usually found on college campuses and office environments. Need a musical hit? Limited groups frequently access a common folder, or shared folders of others they know.
Despite that backdrop, a recent LimeWire upgrade is being tarred with the ‘darknet’ label, based on a feature that allows person-to-person, direct sharing. That coexists alongside more classic, one-to-many (or many-to-one) sharing functionality. In the early days of file-trading, users could frequently access the entire folders of complete strangers, and pick-and-choose contents at will. That feature has been closed (at least as a default function) on many subsequent upgrades, simply because it leaves users overly vulnerable to investigatory eyes (RIAA, MediaSentry, etc.)
On the LimeWire 5.1 build, the private sharing enhancement allows greater privacy and security when the sharer and recipient are already friends. The darker side of that involves copyrighted content, though direct swapping limits the ability to browse and search for plum releases. That usually requires more anonymous searches of connected hard drives, a critical component of the LimeWire experience.
The darknet also runs into logistical problems when file sizes grow. On bigger files like movies, direct sharing can be painstakingly cumbersome, and the BitTorrent protocol significantly reduces the drag by assembling bits-and-pieces from hundreds of disparate files.