We test the relationship between the use of social networking sites (SNS) and a proxy of utility, i.e. subjective well-being (SWB), using instrumental variables. Additionally, we disentangle the indirect effects of SNS on well-being mediated by face-to-face interactions and social trust using a structural equation model. Results suggest that the use of SNS hampers people's well-being directly and indirectly, through its negative effects on social trust. However, the use of SNS also has a positive impact on well-being because it increases the probability of face-to-face interactions. Yet, the net effect of the use of SNS for SWB remains negative.