I remember some documentary about the fiasco at Mogadishu (sp?) as the American troops arrived by helicopter. The American GI\'s were sitting on the side of the copters with their feet dangling. To the people below, showing the sole of your shoe or sandal was an insult to them so a bunch of them took their sandals and showed the GI\'s the bottoms of their sandals. Right off the bat, things weren\'t going well for the Americans.
Cultural protocols can be quite complicated.