I have greatly disliked the word Web 2.0 since it started to be used. It sounded like a bubble waiting to happen since its birth. Today I ran across the very first definition of Web 2.0 that i can relate to and very much subscribe to:

"If you want to see what Web 2.0 really means check out Zopa in the UK or Prosper in the US. These are social lending sites. Both make use of Ajax and pretty colors and both have plenty of collaboration but those things are not the reason I choose these sites to represent the epitome of what I consider Web 2.0. The major revolution with Web 2.0 is what isn't there, and that's middle men.

In the case of Digg what's missing is a formalized news agency. In the case of Flickr it's an editor. The same holds true with Wikipedia. Podcasts bypass radio conglomerates. As for Prosper the missing element is the bank. This extends to the open source community as well. Most open source at least starts out with the same goal so eloquently outlined in The Gettysburg Address:  "...of the people, by the people, for the people..."