I added a short description at the top of the discussion. I've just generalized and extended privacy settings that Facebook and Google+ offer for content residing within their platforms. On the one hand it's possible to assign permissions to web content not embedded in a social utility, on the other, I can provide degree-of-separation ranking of the content users have created, for example comments/reviews. So, out of the hundreds (or thousands) hotel reviews on Tripadvisor, you could get just a bunch, written by people close to you (in a social-network degree-of-separation sense). If I could only get Tripadvisor on board...