As the number of SNSs increases, it is challenging for SNS providers to obtain and retain user loyalty toward a SNS site. By integrating both network externalities theory and VTSL (Value-Trust-Satisfaction-Loyalty) model, we propose a research model to investigate how perceived value derived from network externalities affects trust in SNS site and user satisfaction, which further lead to user loyalty. Data analysis was conducted using a total of 267 responses. The results show that perceived network size and perceived complementarity exert significant effect on functional, emotional, and social value. It is also shown that functional and social value influence positively on trust in SNS site, but emotional value is not related to trust. Functional and emotional value are found to be significant determinants of user satisfaction, however social value is not related to user satisfaction. User satisfaction is found to be a strong determinant of user loyalty. Given the findings, SNS providers need to increase network size and accommodate complementary services, applications, and supporting tools to obtain and retain user loyalty.