You may have seen the following video already as its been doing the rounds for a few weeks now. But if you haven't then I strongly recommend you watch it. Its only 4.5 minutes, so go grab a coffee.
The video is by Michael Wesch, assistant professor of cultural anthropology at Kansas State University. Its a great visual introduction to some Web 2.0 and markup concepts. You can read more about the video here. Wesch has explained that his aim was to "show people how digital technology has evolved and give them a sense of where it might be going and to give some momentum to the all-important conversation about the consequences of that on our global society."