Social networking sites have in the past few years become extremely popular, and have turned the web into a markedly social medium. However, online social networking has led to concerns about privacy, as well as about possible counter-productive effects on making new real-world acquaintances. These effects are, in the short run, aggravated by permanent mobile connectivity. In the long run, however, mobile social networking might actually enhance real-world connections, with persons in your physical vicinity able to introduce themselves on the screen of your handheld. Privacy, anonymity, virtuality, friendship - the topic of mobile social networking clearly invites philosophical, and, in particular, ethical discussions. The volume contains papers by, among others, Charles Ess, Leopoldina Fortunati, Richard Harper, James E. Katz, Rich Ling, and Kurt Röttgers.