Don, I risk reopening the thread you want closed purely on the grounds that you've convinced me: I was making a distinction without a difference.
These "whatever you call 'ems" define what a set of users can do within a location of the site; they involve actors, actions, locations. The different terms being debated emphasize one aspect more or less than others ("communitities" <-> actors; "subsites" <-> locations), but they all represent different blind men touching different parts of the elephant.
It seems likely that if anyone wants to prolong this (a doubtful situation I gather), there might be a term that more satisfactorily captures the three dimensions of meaning implicit in these "whatever you call 'ems". Off hand, I can think of several possibilities: fiefs, sectors, galaxies, realms, firms, confederations...
Granted, most of these are either silly, clumsy or too clever by half, but possibly someone more inventive or better plied with beer can come up with a better term?
Or perhaps the OCT has spoken and this is all moot. Fine by me either way.
