Online Social Networks (OSNs), such as Facebook, Twitter, and Myspace, provide new and interesting ways to communicate, share, and meet on the Internet. On the one hand, these features have arguably made many of the OSNs quite popular among the general population but the growth of these networks has raised issues and concerns related to trust, privacy and security. On the other hand, some would argue that the true potential of OSNs has yet to be unleashed. The mainstream media have uncovered a rising number of potential and occurring problems, including: incomprehensible security settings, unlawful spreading of private or copyrighted information, the occurrence of threats and so on. We present a set of approaches designed to improve the trustworthiness of OSNs. Each approach is described and related to ongoing research projects and to views expressed about trust by surveyed OSN users. Finally, we present some interesting pointers to future work.