OK I have a strong belief that if I'm wearing headphones that it's the universal sign for "Do Not Talk To ME" many people have also confirmed this theory of mine. I make exceptions to the rules, such as the following:
#1 If someone is lost and is asking me for help.
#2 If a friend sees me and starts talking to me.
#3 If I initiate a conversation with someone or potentially gave the person the idea that I was.
With that being said I also wear headphones intentionally when I'm alone on the streets or on a bus so I can keep the hobo's away from me. Well apparently some people are not aware of this sign. I get so irritated with panhandlers talking to me as if I can hear them. I'm not sure what the deal is they are clearly visible.