@stefan @scottjenson Indeed, flexible groups, both private and public, open en closed, seem to have a great potential. (a potential #GooglePlus never managed to sell, but I tend to think this has rather random, non-substantial reasons)
In any case, the popular format of #friends (#facebook) and connections (#LinkedIn) is hard to visualize or define as "circles" really: they constitute a personally unique set of connections that may be displayed much more like neurons, instead.
No matter how complicated to visually imagine, friend-connections (and their popular #platform implementation) make intuitive sense to people and people like to have friends. Most people won't make friends in the current #Fediverse, however.