Currently, I am working on Lockr. Lockr decouples content sharing and delivery from social networks and let's people manage their social relations in a single place and share their personal content across the web and grant access to their friends based on the type of social relationship between them.

We have implemented Lockr Center -- a Facebook application -- for exchanging passes between friends. Passes are digital documents signed by their issuer that can be used to prove existence of a social relationship in its validity time frame. Passes can be used to get access to the personal content of the friends regardless of the system in which the user has shared the content on. We also implemented Lockr for Firefox -- a Mozilla Firefox extension -- that emulates social access control for web sites (currently Flickr is the only supported web site).

Upon first use of Lockr for Firefox, it directs the user to initiliaze his profile on Lockr Center. The user can then go to Flickr and upload socially restricted content. Lockr guarantees that the real socially protected photos are only shown to those who hold appropriate pass from (have appropriate social relation with) the owner of the image. Non-authorized users will see a fake placeholder instead.