In this paper, we focus on social media users and examine the factors predicting users’ confidence in platforms in case of private messaging. For the social media platforms, social ties and information that flows through the contacts are valuable assets, which must be considered in the development of the services (such as messaging applications) in order to attract users. We use nationally representative data derived from surveys targeted at 15- to 74-year-old Finns (N = 3,724). The measures included user’s confidence in platform services in social messaging, trust in social ties on social media, size of social media networks, a wide selection of measures related to internet and social media behavior, and demographic factors. The results of the analysis supported the hypothesis that high confidence in platforms is strongly dependent on the social resources of users. Network size and trust in social ties were crucial variables in determining the confidence in social media platforms as a secure channel of private messages. The results also amplified that trust in social media networks has independent explanation power in the platform confidence apart from behavioral and demographic factors. The findings are significant in terms of understanding the contemporary information society and dynamics between platform services and users. The markets of social media platforms and other agents in the sector are dependent on the social resources of users, and especially on the social trust of users.