Open air urinals in the midst of crowds of people. Unless one lives in a barnyard, certain functions ought to remain private.
Playing devil's advocate, one might ask, why? Why is urination any more disgusting then, for example, shoveling food into your mouth, masticating as you mix it with saliva, and then forcing it down a pipe into the stomach? Or blowing snot out of your nose into a tissue?
I'd agree if we were talking about "#2", but I really don't have any issues with #1.