With the ubiquitous availability of communication devices, personal information and media sharing is quickly becoming one of the key applications on the pervasive Web. In such a context, the publishing and searching of media content heavily rely on the availability of meaningful metadata. The scarcity and heterogeneity of metadata constitute some of the key obstacles preventing meaningful media sharing in large communities. However, participating in a community also opens new perspectives for addressing metadata scarcity and heterogeneity through sharing of metadata and semantic knowledge.