Key Principles of Web 2.0 Applications

In the opening talk of the first Web 2.0 conference, Tim O'Reilly and John Battelle summarized key principles of Web 2.0 applications:
-- the web as a platform
-- data as the driving force
-- network effects created by an architecture of participation
-- innovation in assembly of systems and sites composed by pulling together features from distributed, independent developers (a kind of "open source" development)
-- lightweight business models enabled by content and service syndication
-- the end of the software adoption cycle ("the perpetual beta")
-- software above the level of a single device, leveraging the power of The Long Tail.
-- easy to pick up by early adopters
[Source: Wikipedia, the free encyclopedia: http://en.wikipedia.org/wiki/Web_2]