I'm one of those "ninja" like people. In fact, a few people have called me a ninja due to that. I also have pretty good hearing (I've been told I have "bionic ears"), so I'm not on the recieving end too much. Only 1 person can sneak on me, and both of us have a reputation for being stealthy.
As for the headphones, I use them, but that doesn't stop anyone from talking to me. I also have them turned way down (I can hear the music just fine), so as to hear the ambient noise.