1. Facebook Privacy Policy, http://www.facebook.com/policy.php/
2. Facebook Statistics, http://www.facebook.com/press/info.php?statistics
3. Myspace Privacy Policy, http://www.myspace.com/index.cfm?fuseaction=misc.privacy/
4. Besmer, A., Lipford, H.R.: Moving beyond untagging: Photo privacy in a tagged world. In: Proceedings of the 28th International Conference on Human Factors in Computing Systems, pp. 1563–1572. ACM, New York (2010)
5. Brands, S.A.: Rethinking public key infrastructures and digital certificates: building in privacy. The MIT Press, Cambridge (2000)