Brad Fitzpatrick recently wrote an elegant and important post about the Social Graph, a term used by Facebook to describe their social network. In his post, Fitzpatrick defines "social graph" as "the global mapping of everybody and how they're related". He went on to outline the problems with it, as well as a broad set of goals going forward. One problem is that currently you need to have different logins for different social networks. Another issue is portability and ownership of an individual's information, explicitly and implicitly revealed while using social networks. As was recently asserted in the Social...
Y. Han, and J. Tang. Proceedings of the 21th ACM SIGKDD International Conference on Knowledge Discovery and Data Mining, page 407--416. New York, NY, USA, ACM, (2015)
P. Singer, D. Helic, A. Hotho, and M. Strohmaier. Proceedings of the 24th International Conference on World Wide Web, page 1003--1013. Republic and Canton of Geneva, Switzerland, International World Wide Web Conferences Steering Committee, (2015)
F. Kooti, N. Hodas, and K. Lerman. Proceedings of the eighth International AAAI Conference on Weblogs and Social Media, page 266--274. AAAI, AAAI Press, (June 2014)
X. Wen, Y. Lin, C. Trattner, and D. Parra. Proceedings of the 25th ACM Conference on Hypertext and Social Media, page 285--290. New York, NY, USA, ACM, (2014)