File sharing has long been a popular use of the Internet. I remember sitting at my laptop and asking a friend to name a song, and then seeing if I could download it off of Napster and play it before he could find the cd on the shelf, put it into the player and play the song himself. I often won those competitions.
The old Napster is long gone, but was of course replaced with many other P2P networks. Today, a significant portion of Internet traffic is comprised of files being moved over bittorent, a popular and completely decentralized way of sharing files.
Bittorent, though, requires some basic technical knowledge and is neither anonymous nor safe. The RIAA and MPAA routinely monitor these networks and attempt to collect IP addresses of computers they believe are involved in the transfer of copyrighted files. And bittorent is notorious for transferring files that (sometimes) contain viruses, spyware and other malware.
Enter private file sharing networks. WASTE was released in 2003 and allowed people to create private networks among trusted friends. Files could be shared without worrying about malware or prying eyes. All that was needed was trust among the members of a particular network. The downside of WASTE was that setting up and participating in a network was not trivial to do. Private networks did not take off and achieve mass use and adoption.
A new crop of services has popped up recently to make it much easier to share files with a private network of friends and other trusted people. Allpeers, Zapr, Pando and Exaroom are all fairly recent entrants.