"While The Pirate Bay and other public sites get the most news coverage, the momentum now is toward the private torrent communities: Websites that are accessible by invitation only, have strict rules about sharing and etiquette and usually focus on a single type of pirated content, such as music or films.
PassThePopcorn.org, as the name implies, tracks only files for downloading films but offers everything from the lowest resolutions all the way up to the high-definition quality available on Blu-ray discs. To join, you have to be invited by a current member.
The What.cd community, operating on a similar model, shares more than 270,000 musical albums representing 140,000 bands, according to internal statistics posted on its website.
Mike Masnick, CEO of research firm Techdirt, say that while private BitTorrent trackers are proliferating, it is difficult to directly assess this growth. Shrouded in secrecy, private trackers are illegal and try not to attract attention.
In a widely publicized incident in 2007, private community Oink.cd — whose members famously included Nine Inch Nails frontman Trent Reznor — was raided by international police organization Interpol, and a few of its members were charged with copyright infringement." (http://www.usatoday.com/tech/news/2009-06-23-online-files-napster_N.htm)