I'm a TSA screener at PHL and understand how you may feel it is disrespectful for a stranger to address you by your first name, but there are alot of people who don't feel this way and think of it as just a way of being friendly. I can think of a few incidents right away. There is a male passenger that comes through my checkpoint at least twice a week. He is a VP for BJ's Wholesale Club and lives in suburban Philadelphia, but his office is outside of Boston. We are all on a first name basis with him and always engage in conversation with him. We talk about the weather, sports, how our or his vacation was, etc. More than a couple of times other passengers have observed this and commented about how nice it was to witness someone having such a nice, friendly experience while trying navigate the checkpoint compared to the dull, tense, "move it along" scene usually witnessed. I usually just refer to people as sir or maam, but there are a few exceptions to that if I recognize the person as a frequent flyer or if the person addresses me by name. I guess it just depends on the person. Some find it disresectful, some think it's nice. When I was in high school, I worked at a restaurant and we were taught that it was good customer service to address repeat customers by name.