Having started with a single video of a trip to the zoo in April of last year, YouTube now airs 100 million videos–and its users add 70,000 more–every day.

What happened? YouTube’s creators had stumbled onto the intersection of three revolutions. First, the revolution in video production made possible by cheap camcorders and easy-to-use video software. Second, the social revolution that pundits and analysts have dubbed Web 2.0. It’s exemplified by sites like MySpace, Wikipedia, Flickr and Digg–hybrids that are useful Web tools but also thriving communities where people create and share information together. The more people use them, the better they work, and more people use them all the time–a kind of self-stoking mass collaboration that wouldn’t have been possible without the Internet. | The third revolution is a cultural one. Consumers are impatient with the mainstream media. —Best Invention: YouTube (Time)