Now that our communications technology is changing, the distinctions among those patterns of comunication are evaporating; what was once a sharp break between two styles of communicating is becoming a smooth transition. Most user-generated content is created as communication in small groups, but since we're so unused to communications media and broadcast media being mixed together, we think that everyone is now broadcasting. This is a mistake. (Shirky 2008: 87)
Shirky, C. (2008). Here Comes Everybody: The Power of Organizing without Organizations. New York: The Penguin Press.
Quick postscriptum - a nice new term for UGC is "indigenous content"