Social software is a class of information systems supporting the establishment and management of online communities for people in performing certain tasks. One of the first application types were bulletin boards. Social software may provide different services for community members such as finding members with similar interests, finding information on interesting subjects, discussing common problems, or simply the storing of private or publicly-accessible documents. Another similar term, collaborative software, applies to cooperative work systems, and is applied to software that supports working functions often restricted to private networks. Web 2.0 is a term coined only recently, and with this concept promoters try to focus on the change of use of the Internet. While Web 1.0 was a medium where few users published information in Web sites and many users read and surfed through these publications, in Web 2.0 many users also publish their opinions, information, and documents somewhere in the Internet. By motivating large communities for submissions and by structuring the content, the body of the aggregated information achieves considerable worth. A good example for such a community project is Wikipedia, where thousands of contributors deliver millions of articles, forming an encyclopaedia that is worth millions of dollars.