Introduction
The development of information and communication technology (ICT) such as the diffusion of smart phones have become a reality, meaning that all things are connected to a network and people are free to access the Internet anytime, anywhere. These days, the Internet is being offered free of charge in many areas and a new type of Internet service called "platform services" is becoming popular. These platform services have started collecting and managing various types of users' personal information which including searching, commenting, and networking (Bauer et al., 2012; Duan et al., 2020; Valletti & Wu, 2020). Platform operators who...