I hate it when people wear headphones when they're with someone else.
I saw it today when my parents and I went for a walk. As we were on our way back to the car, we passed two people who were just starting out. They both had headphones in, but they were talking, so they were having to yell over the sound of their music.
My dad, who was walking behind me and my mom, thought the woman was talking to us because she was talking so loud.
I do, however, understand if you want to concentrate while you're running, so I'll let this one slide, I guess.
Even worse, though: I also saw a couple walking around together in Old Navy the other day with their headphones in. Like, what are you doing? Why do you need to constantly be listening to music? Or are you leaving your headphones in just in case you get a phone call?
Seriously, guys. Just put your headphones away and talk to the person you're with!