Thx to DavidPalm. Rad full article: http://www.darwinmag.com/read/050103/social.html

What is Social Software?
People naturally tend to use software as a means to advance personal interests and to interact socially. As a result, the most broadminded consider the "cc:" line on e-mail the starting point of social software; others restrict the term a bit more. In fact, you may be tempted to ask, "what isn't social software?"

I believe the phrase social software should be more helpful, and can distinguish software built around one or more of these premises:

1. Support for conversational interaction between individuals or groups — iincluding real time and "slow time" conversation, like instant messaging and collaborative teamwork spaces, respectively. This is also supported by the interplay always going on in blogs, where one blogger riffs on something another has said, and a third jumps in with more commentary, and the next thing you know, 40 others chime in, and someone suggests creating a groupblog to pursue the theme, whatever it may be. A big freewheeling discussion, with snippets of the interaction spread all over the place.
   
   
2. Support for social feedback — which allows a group to rate the contributions of others, perhaps implicitly, leading to the creation of digital reputation. Digital reputation — also known as karma (from the Slashdot web community model) or whuffie (from Corey Doctorow's science fiction novel, Down and Out In the Magic Kingdom) — will turn out to be an area of great importance. Consider the lengths that eBay sellers go to to maintain a good reputation.
   
   
3. Support for social networks — to explicitly create and manage a digital expression of people's personal relationships, and to help them build new relationships. These usually involve some sort of "six degrees of separation" system. One example is the Friend Of A Friend (FOAF) proposed standard, an XML-based approach to define your interests, phone number, e-mail, and the degree and kind of relationships you have with others, including creating explicit links to their FOAF specifications (which, of course, refer to others' FOAF definitions, and so on). The heady interest in Web-based services like Ryze, Friendster, LinkedIn and others, which are explicitly social (or business) networking systems, is being driven by a growing awareness of the fluidity and flexibility of networking through the Internet.
   .... http://www.darwinmag.com/read/050103/social.html