Why do people share their context information on Social Network Services? A qualitative study and an experimental study on users' behavior of balancing perceived benefit and risk

•Perceived expected benefit influences on users' intention to share context information more than risk does.•Too high perceived expected risk is undesirable, but also risk need not to be too low if it reduces benefit.•Only perceived expected risk differ with the context information type.•Users employ not only the means provided by system but also various kinds of manual controls.

Despite the rapid growth of context-aware systems and ubiquitous computing, the factors influencing users' decision to share their context information in a social setting are poorly understood. This study aims to clarify why users share their context information in social network service (SNS), even while they are concerned with the potential risk at the same time. Drawing on the diverse theories of self-disclosure, we take an approach that the consideration of benefit encourages users to endure the existence of risk, and that users actively adjust the way they share their information to optimize the level of benefit and risk. In a qualitative study, we examined what kinds of risks and benefits exist in context information sharing situations and how users control them. An experiment was conducted using stimuli that simulate the actual use of SNS to investigate the effect of various context types and control types on users' expected benefit and risk and their intention to share. The results showed that both expected benefit and expected risk influenced users' intention to share. More interestingly, the effect of expected benefit was found to be stronger than that of expected risk. Moreover, different privacy control strategies were found to have induced different effects on the expected benefit and expected risk. Implications and limitations of this study were proposed at the end of this study.