Netflix accounts for 30% of all downstream internet traffic in the US

"Netflix video streaming is now the single largest source of peak downstream Internet traffic in the U.S., according to a new report by Sandvine. The streaming video service now accounts for 29.7 percent of peak downstream traffic, up from 21 percent last fall.
That puts Netflix above HTTP websites (18 percent), BitTorrent (11 percent), and YouTube (10 percent) as a source of downstream traffic during peak times in North America. (BitTorrent still accounts for half of all upstream traffic). As whole, “real-time entertainment” (which is mostly video streaming, but also includes streaming music) accounted for 49 percent of downstream traffic in March, 2011, versus 19 percent for P2P file sharing, and 17 percent for Web browsing.
Video files are so big that it does not take much usage for it to take over in terms of bandwidth consumed. But these numbers definitely point to a future where video accounts for more and more of the traffic on the Internet. As recently as last November, Web video alone accounted for an estimated 37 percent of Internet traffic."

Source:  Data from Sandvine, reported by TechCrunch, 17th May 2011