Mobile social networks (MSNs) are specific types of social media which consolidate the ability of omnipresent connection for mobile users/devices to share user-centric data objects among interested users. Taking advantage of the characteristics of both social networks and opportunistic networks, MSNs are capable of providing an efficient and effective mobile environment for users to access, share, and distribute data. However, lack of a protective infrastructure in these networks has turned them in to convenient targets for various perils. This is the main impulse why MSNs carry disparate and intricate safety concerns and embrace divergent safety challenging problems. In this paper, we aim to provide a clear categorization on safety challenges and a deep exploration over some recent solutions in MSNs. This work narrows the safety challenges and solution techniques down from opportunistic networks (OppNets) and delay tolerant networks (DTNs) to MSNs with the hope of covering all the work proposed around security, privacy and trust in MSNs. To conclude, several major open research issues are discussed and future research directions are outlined.