Men's Urinals and Antiferromagnetic Equilibria

In the men's room, there is an understanding: you space as far apart from each other as possible at urinals. Not doing so, or when some gaps must be filled, leads to frustration --- not just in real life but also in the sense of spin models from statistical physics.

The stable equilibrium in this case is most definitely the antiferromagnetic one.

(Also, you are not supposed to talk. Ever.)

Update: Aaron Clauset reminds me of the related discussion and mathematical formulation in xkcd.