The problem of trust is one of the more prominent security issues in online communications. In this thesis, we propose a new security threat model, computer mediated introductions (CMI), where individuals are introduced online for the purpose of interacting offline. This is a problem that has not been specifically studied in the literature, even though aspects of it have been covered elsewhere. We therefore critically analyze the issue of trust and reputation in CMIs with the aim of improving trust on these platforms. In one of the most popular forms of CMI today, online dating, our findings show that existing standard mechanisms are not sufficient to establish meaningful trust on the platform. While we propose some potential alternative mechanisms for establishing trust in CMIs, the key contribution of this work is to identify the security challenges that arise in computer mediated introductions as a previously unrecognized class of security problems.