I get this from Wikipedia:
To some extent Web 2.0 has become a buzzword, incorporating whatever is newly popular on the Web (such as tags and podcasts). A consensus on its exact meaning has not yet been reached.
Until somebody explains just what it is, I'm not going to be afraid, especially not by somebody who's just throwing out names like Marx, Spengler, Kafka, Bono, and Mozart to show off.
To some extent, Keen's nightmare has already happened. Fifty years ago everybody lined up for Hitchcock or John Wayne or Gregory Peck movies. Today when you go into a video store there are hundreds of new pictures by unknown directors. It doesn't mean that the movies are getting worse, just that it's hard to know who's who.
Chaos is here, like it or not. I really doubt big media of one sort or another are going to crawl up and die or the heavens will fall because outsiders get more of an audience on the Internet.
This map of Web 2.0 companies also has a good set of links to "best of Web 2.0" sites and projects, down on the lower right column.
http://www.fourio.com/web20map/
By poking around on the sites anyone can see that Web 2.0 has absolutely nothing to do with the bloviating nonsense Keen describes.