"Two things define the essence of Web 2.0: 1) social network software, and 2) services on the web. And the common denominator between these two is collaboration.
At the center of social networks software are human relationships and interactions that are facilitated through web portals, providing easy access and sharing to/with others - the ability collaborate with others. (...)
Services on the web is the foundation, the engine, the platform that fuels today's (and the future) web - this is software developed as services. And these services are the new platform..."