Introduction Today, the term Web 2.0 is used to describe applica- tions that distinguish themselves from previous generations of software by a number of principles. These new, Web 2.0, applications take full advantage of the network nature of the Web: they encourage participation, are inherently social and open. Whereas Web 2.0 is not characterized by a new step of technology as is the Semantic Web [10], in the last years the Web changed from a medium to a platform, from a read-web to a read-write-web, thereby fulfilling Berners-Lee’s original vision of the Web [9].