As a web or virtual construct, knowledge communities can be said to have evolved from bulletin board systems, web forums and online discourse communities through the 80s and 90s. When framed with the scores of social networking sites coming online at the turn of the millennia, knowledge communities can be described as another form of social media. The biggest difference between social network sites and knowledge communities is, social network sites typically lack moderation or an outcome orientation. Social knowledge management technologies such as Knowledge Plaza are emerging and aim at reconciling these differences.