Distance kept from others is also has a very strong cultural component, we have the same concept of personal boundaries but we measure them differently - the norms established by what is acceptable in where we live.
So we have basically 2 types of scenarios here:
I. One that involves people from different cultural backgrounds (e.g. people who live in a city VS people who grew up in rural places). In such case there might be a type of cultural clash - someone is not going to be happy about the distance kept and will try to fix it by moving closer or away.
II. The other case is when both sides are from the same background; in such event the distance the parties keep can teach you a lot about their relations - physical nearness is obviously an indicator to an emotional bond, but also to the amount of comfort and social respect.
We can also include in this section any haptic information (meaning "that of a touch") you might observe.