Web 2.0 is a very misused term and has been relegated to the 'buzz word' bin by many. The crux of the idea is "network as platform" as explained by Tim O'Reilly the event organiser of the Web 2.0 Summit.
These videos from the recent Summit are really worth a look for an insight into what Bob Sutor from IBM describes as an "inflection point" in the development of the web. Other speakers include Al Gore and Mark Zuckerberg from Facebook. Shai Agassi discusses his electric car concept which has backing from Renault, Israel and Denmark! Interesting stuff.
Check out the vids and visit the website.
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