The rapid growth of the online social network sites (e.g. Facebook, Twitter, LinkedIn, and Google+) and their publicly available data acquiring API has led the prosperity of social network analysis research these days. One of most popular topics of the social network analysis is identifying influential users and their ‘‘network impact’’. Knowing the influence of users and being able to predict it can be leveraged for many applications. The most famous application to researchers and marketers is viral marketing, which aims at targeting a group of influential users to maximize the marketing campaign ROI (Return of Investment).