In his Pattern Language, Christopher Alexander described the pattern Intimacy Gradient.
In his Life with Alacrity blog, Christopher Allen generalizes the pattern to cover issues of trust in online communities and social software.
The pattern appears as a set of discrete steps. (Thus the bedroom is more intimate than the drawing room, which is more intimate than the front porch.) This is consistent with Chris Alexander's favouring of discrete transitions (e.g. the Entrance Transition pattern).
The pattern is undoubtedly much better than the crude binary classifications imposed by machines and bureaucracies (trustworthy/non-trustworthy), But does it fully reflect our human experience? Do we trust people in discrete steps - in leaps and bounds, as it were - or as a continuous process?