People think they can do whatever they want.  In the airport the other day, a guy took his shoes off and put his foot up on his knee, so that his sock-covered foot was ominously close to the face of the person sitting right next to him.  I know people in other cultures can't quite grasp the idea of personal space, but this is more than just space.  People in America have a general hatred of feet.  A good way to insult someone is to put your bare foot on them.  You'll always get a "Gross!" 

I used to eat lunch with a guy who used to take a big bite of food and then just let the undesirable pieces fall out of his mouth and back onto his plate.  I had to try pretty hard not to throw up.  Maybe that was an acceptable thing to do in his homeland of Africa, but we don't do that here in America.  But it wasn't like having a big bite of spaghetti and letting some fall out of your mouth after you bite it in half.  It was like eating a salad and just pushing the romaine lettuce out of your mouth with your tongue, kind of like how a baby drools.  Or it's like eating meat and spitting out a piece of fat, but doing it in plain view. #sociology