adj. Describes a technology or system that enables individuals to deal with each other directly without requiring a central organizing point or authority.
The RIAA and the labels took an aggressive stance as soon as online music file sharing became popular. They won an early victory in 2001 by shutting down the seminal music-sharing service Napster.

The site was an easy target because Napster physically maintained the computer servers where illegal music files, typically in high-fidelity, compressed, download-friendly MP3 format, were stored. [With P2P networks, the files are stored on individual user computers; special software lets consumers "see" the files and download them onto their own hard drives.]
—Daphne Eviatar, “Record industry, music fans out of tune,” The Recorder, August 20, 2003
The tchotchke transfers have also helped make X.com the Web's leading financial site, with more than 2 million weekly unique visitors — more than double the traffic of E-Trade, the nearest competitor. . . . So it's no wonder that dozens of companies are tripping over themselves to get into the person-to-person, or 'P2P' payment race.
—Noah Shachtman, “Does P2P Fit Consumers' Bill?,” Wired News, June 12, 2000
1970 (earliest)
A famous Chinese saying states a man should be steadfast at the age of 30. When Zhang Shishi, Yang Yifu and Li Xinhe turned 30 this year, they were definitely steadfast regarding their business of peer-to-peer lending, known as P2P.
—Hu Yuanyuan, “Three P2P pioneers take stock at 30,” China Daily - Africa Weekly, January 01, 1970