January 2009 data from the comScore Video Metrix service showing that U.S. Internet users viewed 14.8 billion online videos during the month, representing an increase of 4 percent versus December 2008.YouTube led the growth charge, accounting for 91 percent of the incremental gain in the number of videos viewed versus December, as it surpassed 100 million viewers for the first time.

http://www.comscore.com/press/release.asp?press=2741