I've run every event over my high school career, from 100-3200, as well as 5K xc. There is a very hard cutoff between 400 and 800. 100-400, no one shakes hands, while 800 and up is usually a lot friendlier and sportsmanlike. Not sure if it is because of the types of people these different events attract, or just because of the nature of finishing in lanes. 100 and 200 do tend to have more macho/jock types.
On a related note, distances races tend to be much friendlier while waiting before the races. Everyone knows each other and jokes around as friends. 400 and down, however, consists more of everyone acting tough and staring each other down before the race, and trying to play some sort of mind games.
These are just my observations and could vary regionally or at different levels of competition.