Abstract-Social networking sites obtained a great success in the last years. Their popularity is related to changing lifestyles, where people increasingly look for new acquaintances or cultivate old friendships by means of the Internet, typically using a PC. Yet along with the rapidly increasing amount of mobile phone users, as well as the development of so-called smart phones, the possibility for creating similar services for mobiles arises. Importantly, the mobile phones are not just entry points to existing social networks with their centralized architectures; being mobile offers one more degree of freedom. However, mobile social network services are unquestionably limited by mobile phones weaknesses (e.g. small screen, keyboards), so several challenges are necessary to be addressed. Consequently, in this paper we analyze usability and user satisfaction of mobile social networks. Thus, a mobile social network application called Spiderweb is implemented and used as a test case. Spiderweb provides to the users an opportunity to make acquaintances, search for people on the basis of certain criteria, chat, view profiles of other users, and with numerous other possibilities. Yet the application not only offers the mobile phone users services similar to social networks available on the web. Spiderweb moves beyond this concept, also giving an opportunity to interact with other users through Bluetooth connectivity. Thus, the application enables establishment of spontaneous collaborative networks which are further explored and evaluated in this paper.

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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 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 analyzing results of an empirical investigation comprising of 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.

Despite the great success of online social networks, there is still no automated way to facilitate communication between people in the physical environment. Ubiquitous social networking services target at transferring online social networking benefits to the physical world, by facilitating advantageous relationships during physical meetings between people who do not know each other, but probably they should. In this paper, we present a potential solution for establishing ubiquitous social networking services by integrating online social networks with opportunistic networks. This solution, called local social networks, focuses on uncovering relevant connections between people nearby, by providing a platform for automatic exchange of user personal information in order to discover interpersonal affinities. Firstly, we define and discuss the concept, advantages, preliminary architecture and potential future applications of local social networks as well as introduce the first prototype, named Spiderweb. Afterwards, we present results of a qualitative investigation that researched whether 16 active online social networks users would accept ubiquitous social networking services. The results revealed that all the participants perceived the usefulness of these services and 14 of them would be willing to accept all the necessary requirements for the establishment of local social networks and consequently be potential users.

Abstract-Privacy has already been identified as the main threat to long-term success of ubiquitous computing, especially in environments, which target at promoting ubiquitous social networking. Notably, these environments are founded on disclosure of personal information and thus, the amount of data disclosed is directly proportional to potential networking benefits. The networking advantages would be maximized by sharing all available personal data, however this would result in jeopardizing of users' privacy and a compromise is necessary. Consequently, privacy management systems of ubiquitous computing must be capable of disclosing only personal data, which is relevant, however not sensitive in specific circumstances. In this paper we provide insight into human personal data sensitivity and disclosure decisions by presenting results of an online survey regarding respondents' willingness to share their personal information under different circumstances. We believe that our findings provide relevant inputs for the design of management privacy models in ubiquitous computing.