Social exchange theory proposes that social behavior is the result of an exchange process. The purpose of this exchange is to maximize benefits and minimize costs. Online social networks seem to be an ideal platform for social exchange because they provide an opportunity to keep social relations with a relatively low cost compared to offline relations. This theory was verified positively many times for offline social interactions, and we decided to examine whether this theory may be also applied to online social networks. Our research is focused on reciprocity, which is crucial for social exchanges because humans keep score, assign meaning to exchanges, and change their subsequent interactions based on a reciprocity balance. The online social network platform of our choice was Facebook, which is one of the most successful online social sites allowing users to interact with their friends and acquaintances. In our study we found strong empirical evidence that an increase in the number of reciprocity messages the actor broadcasts in online social networks increases the reciprocity reactions from his or her audience. This finding allowed for positive verification of the social exchange theory in online communities. Hence, it can be stated that our work contributes to theories of exchange patterns in online social networks. 
Social exchange in online social networks. The reciprocity phenomenon on Facebook