The Internet based solutions have developed rapidly in the last decade. Online social networks are among the most popular solutions. The capabilities of mobile phones enable to reach social networks via different interfaces. However, it is an open question how to involve them efficiently in the social network architecture. We should realize the fact that the phonebook of the mobile device describes the social relationships of its owner. Based on that, relationships can be discovered automatically. Content distribution is becoming more and more important in social networks. BitTorrent is one of the most efficient peer-to-peer based content distribution solution. Involving mobile phones into such network is challenging, however it has great benefits e.g. when applying such architecture in mobile related social networks. This book addresses these issues and proposes novel and efficient approach considering mobile environment. The book brings several practical examples and real measurements to help understating the results.