We add to the literature by conducting the first empirical assessment of how online networking affects two economically relevant aspects of social capital, i.e. trust and sociability, in a large and representative sample. We address endogeneity in online networking by exploiting technological characteristics of the pre-existing voice telecommunication infrastructures that exogenously determined the availability of broadband for high-speed Internet. We find that participation in SNSs such as Facebook and Twitter has a positive effect on face-to-face interactions. However, social trust decreases with online interactions. We argue that the rising practice of hate speech may play a crucial role in the destruction of trust.