I'm trying to develop http://www.cawtech.demon.co.uk/outer-circle/core.html around the idea of shared hierarchical white lists.

this avoids narrowness because you can set the tree depth deep enough to put lots of people on your whitelist.

Scobleizer complains about the other people inviting other people into your life. Outer Circle suffers from this problem, but you do get to control who gets to invite other people into your life.