Nowadays, mobile social networks are capable of promoting social networking benefits during physical meetings, in order to leverage interpersonal affinities not only among acquaintances, but also between strangers. Due to their foundation on automated sharing of personal data in the physical surroundings of the user, these networks are subject to crucial privacy threats. Privacy management systems must be capable of accurate selection of data disclosure according to human data sensitivity evaluation. Therefore, it is crucial to research and comprehend an individual's personal information disclosure decisions happening in ordinary human communication. Consequently, in this paper we provide insight into influential factors of human data disclosure decisions, by presenting and analysing results of an empirical investigation comprising two online surveys. We focus on the following influential factors: inquirer, purpose of disclosure, access & control of the disclosed information, location familiarity and current activity of the user. This research can serve as relevant input for the design of privacy management models in mobile social networks.