http://www.tgdaily.com/software-features/53728-just-100-users-responsible-for…
A team at Carlos III University of Madrid examined the behavior of users who published over 55,000 files on the two main portals of BitTorrent, Mininova and The Pirate Bay. They collected the names, ISPs and IP numbers of publishers, and the IP numbers of downloaders.They found that just 100-odd users were responsible for 66 percent of content published and 75 percent of downloads.