I don't know about amplification, but recorded entertainment de-sensitises people. No one on a TV program or radio complains if you decide your conversation is more important than the show. Some people don't realise there's a difference between 'canned' and live entertainment.

I've noticed, along with an increase in rudeness, a decrease in others' willingness to do something sensible about it. Folks will do almost anything to avoid direct confrontation. People will spill drinks on folks, shoot spitballs, glare, or get up and leave - anything except ask the offenders to please quiet down. There's no excuse for rudeness, but we all do things that irritate others, and we're all imperfect. I would hope if I were doing something I wasn't aware was obnoxious (probably because I was lost in my own little world) someone would kindly point it out. I wouldn't have a problem with that. I would have a problem with someone avoiding conflict right up until they couldn't take it anymore and blew up at me. (This hasn't happened to me, but I've seen it happen gazillions of times.) It's an indiviual's responsibility to learn 'rules' of acceptable behaviour. It's society's responsibility to let individuals know what the rules are, and enforce them.