A lot has been written about YouTube on the Web. Here's what I've found most informative to date. If you know I missed something, please let me know!

YouTube Statistics

• Michael Wesch's anthropologic study of YouTube (March 2008)
• comScore: YouTube Surpasses 100 Million U.S. Viewers for the First Time (March 2009)
  

YouTube Theory

• List of articles by subjects at Watching YouTube