The demand of new Social Networking Service (SNS) is high because the SNSs have been popular these days. In order to deliver various SNSs as early as possible, software product line (SPL) approach can be useful. By using the state of the practices of SPL, this paper shows how to manage commonalities and variabilities of SNS. Specifically, to make an architecture design, presented practices include: understanding relevant domains, requirements engineering, architecture definition. The strengths and weaknesses of Face book architecture are evaluated with the Architecture Tradeoff Analysis Method (ATAM). As a result of applying a framework for SPL practice, layered view and component-based view are illustrated along with variabilities represented by Product Line UML-based Software Engineering (PLUS) and Orthogonal Variability Model (OVM). Based on the analysis of requirements of SNS, additional services such as file sharing and instant messaging are represented as optional components. In case of Face book, three key quality attributes, i.e., availability, scalability, and privacy are analyzed by using quality attribute utility tree. We identified that Face book employs client-server architecture. Through ATAM, Peer-to-Peer (P2P) approach promoting privacy is explained.