Decentralizing Social Networking Services

Online Social Networks (OSN) of today represent centralized repositories of personally idenfiable information (PII) of their users. Considering their impressive growth they arguably are the most popular service on the Internet, both by technology savvy but even more by comparibly inexpert audiences, today. Being voluntarily maintained and automatically exploitable, they are a promising and challenging target for commercial exploitation and abuse by miscreants. Several approaches have been proposed to mitigate this threat by design. Removing the centralized storage, they distribute the service and data storage, to protect their users from a provider that has access to all the information users put into the system. This paper gives an overview of currently proposed approaches, and classifies them according to their core design decisions.