In CSCW we are researching support for collaboration in work groups for several decades now. Web 2.0 and Social Software entered this field from another starting point recently, and quickly expanding towards support for collaboration in enterprises (Enterprise 2.0). However, the interaction between both fields is minimal. In this paper I am trying to contribute to bridging the gap by identifying the core contributions of the two fields, and how they can be integrated or used to the benefit of both fields.