Basically, the concept encompasses all the new-ish "web services" that are available now - those sites where almost all of the content is user-provided and interactive. This includes Wikipedia, social network sites like Friendster, and all those other sites you may visit that highly encourage you to add a lot of stuff. (If you want more info about this, check out the moderator's slides: http://howardgreenstein.com/Web2final2.pdf)
In a certain sense these blogs are similar. Google (or whoever) runs the website, but the users/visitors add all the content that makes them meaningful for others to visit and read/add content. All Google provides is the technological framework.
So the discussion swirled around monetization, marketing hype, and who benefits. Anyway, an interesting discussion and we'll see where it all goes.
Originally posted to floydinnovations.blogspot.com, transferred 12/11/2009