Many in the marketing world are trying to understand web 2.0. There's no consensus on what exactly Web 2.0 is, except that it's transformative. This video produced by Dr. Michael Wesch at Kansas State's Anthropology department is the most compelling description I've seen so far (be sure to turn up the volume for the full experience):
Web 2.0 will transform culture in many ways. How will Web 2.0 transform marketing? It's evolving quickly. What do you think?