People are so obnoxious with their cell phones. I can totally see people seated in one section of the plane calling a friend/sibling/coworker seated elsewhere on the same friggin plane.
It's bad enough on trains. I have no idea why people scream into cells, or why they have no concept that what should be their private business is being heard by everyone.
A few years ago, a woman behind me on the Metroliner to New York was getting some work done on her beach house, making appointments on her cell phone. By the end of half an hour, I knew where her house was, where she kept the keys to it, what days she would and would not be there, and two of her credit card numbers. I could have taken over her whole life and she would never have been able to figure out how her identity - and a lot of her belongings - got stolen.
People are becoming increasingly obnoxious in all walks of life. There is, of course, the people ruining your meal/movie/plane ride with their loud cell chatting. There are also people who curse in public or who loiter in the left lane of the highway preventing people from passing. What all these folks have in common is their obliviousness to others.