Clay Shirky has posted an interesting blog entry called, Social Software and the Politics of Groups, which looks at the political approaches, group experiences, and barriers to public development of tools such as weblogs, wikis, chat and instant messaging by comparing these to old systems and old assumptions.
Social Software are different when compared to other traditional groupware and knowledge management tools, which are based on pre-defined roles, workflows, and categories.
A company that provides such a service is SocialText.