The use of online communities has been growing noticeably over the past years. Within only a few months, services like Twitter1, Facebook2 or XING3 have gained several million of users. It is, however, not quite obvious what makes these platforms that attractive to so many users and what factors motivate them to engage very intensively in these environments. In our opinion, the possibility of building social relationships with others might be one aspect: Most systems offer mechanisms that show the ‘rank’ or ‘social reputation’ users have earned. The question is, how important is this ‘reputation’ for users, how actively do users they try to gain social reputation in virtual worlds and to what extent can this be described as a reward mechanism that influences a user’s behaviour?
In the following we will illustrate the users activities in gaining social reputation and its management by regarding the microblogging network Twitter. The objectives of this chapter are on the one hand to give an overview about the various scenarios of Twitter use and on the other hand to outline a theoretical construct dealing with reputation in social networks. This includes the definition of reputation in these networks and introduces the findings of a study which was conducted in order to find out to what extent Twitter users undertake activities for gaining online reputation. We will also deal with the question, whether this reputation mechanism influences users’ behaviour in relation to learning.