Social networks such as Facebook, Twitter and Google+ have attracted millions of users in the last years. One of the most widely used social networks, Facebook, recently had an initial public offering (IPO) in May 2012, which was among the biggest in Internet technology. Forprofit and nonprofit organizations primarily use such platforms for target-oriented advertising and large-scale marketing campaigns. Social networks have attracted worldwide attention because of their potential to address millions of users and possible future customers. The potential of social networks is often misused by malicious users who extract sensitive private information of unaware users. One of the most common ways of performing a large-scale data harvesting attack is the use of fake profiles, where malicious users present themselves in profiles impersonating fictitious or real persons. The main goal of this research is to evaluate the implications of fake user profiles on Facebook. To do so, we established a comprehensive data harvesting attack, the social engineering experiment, and analyzed the interactions between fake profiles and regular users to eventually undermine the Facebook business model. Furthermore, privacy considerations are analyzed using focus groups. As a result of our work, we provided a set of countermeasures to increase the awareness of users.