The biggest challenge in fostering a virtual community is the supply of knowledge, namely the willingness to share knowledge with other members. This paper integrates the Social Cognitive Theory and the Social Capital Theory to construct a model for investigating the motivations behind people's knowledge sharing in virtual communities. The study holds that the facets of social capital — social interaction ties, trust, norm of reciprocity, identification, shared vision and shared language — will influence individuals' knowledge sharing in virtual communities. We also argue that outcome expectations — community-related outcome expectations and personal outcome expectations — can engender knowledge sharing in virtual communities. Data collected from 310 members of one professional virtual community provide support for the proposed model. The results help in identifying the motivation underlying individuals' knowledge sharing behavior in professional virtual communities. The implications for theory and practice and future research directions are discussed.

The article analyzes how community members who were evacuated from their homes use various media, and especially the internet, to keep in touch, receive and disseminate information and express their opinions. Of particular interest are the differences between members of various groups, who differ in their decision whether to relocate in Israel with the rest of the original community or not, in media usage patterns and sense of community. The findings demonstrate that evacuees use diversity and multiplicity of media, where various media are used for different purposes according to need. Small media, with a rather limited and local reach (such as pamphlets, SMS, niche websites and small-scale meetings) are predominantly used for most of the needs, overshadowing mass media usage. Correlations were found amongst various media usages, and between the usage of various media and users’ sense of community. The study demonstrates how contemporary media users use a variety of media depending on their circumstances and needs, and how media usage assists in establishing and maintaining a sense of community after the forced transition from the communities of origin.