Being rational or aggressive? A revisit to Dunbar's number in online social networks

Recent years have witnessed the explosive growth of online social networks (OSNs). They provide powerful IT-innovations for online social activities such as organizing contacts, publishing content, and sharing interests between friends who may never meet before. As more and more people become active users of OSNs, one may ponder questions such as (1) Do OSNs indeed improve our sociability? (2) To what extent can we expand our offline social spectrum in OSNs? (3) Can we identify some interesting user behaviors in OSNs? Our work in this paper attempts to answer these interesting questions. First, we systematically validate the existence of a new Dunbar's number in OSNs, which is ranging from 200 to 300 empirically. To reach this, we conduct local-structure analysis as well as user-interaction analysis on extensive real-world OSNs. Second, based on this new number, we divide OSN users into two categories: the rational and the aggressive, and find that rational users intend to develop close and reciprocated relationship, whereas aggressive users have no consistent behaviors. Third, we propose a simple model to highlight the constraints of time and cognition that may affect the evolution of OSNs heavily. Finally, we discuss the potential use of our findings for viral marketing and privacy management in OSNs.