patternlanguageforthesocialnetwork__intimacygradient

Lot of discussions about IntimacyGradient at the moment. To enable groups to sustain themselves there needs to be a notion of degrees of intimacy or membership. What ClayShirky (in CreatingCommunities) calls a "core" group who have rights (and responsibilities?) that trump the casual / ordinary member of the community. How does software represent this transition between casual and core membership?