Demise of social interaction?

I was on my way home today when I was approached by a girl canvassing for some data collection agency. She was apparently collecting data to canvass opinions on train travel and effects of winter on travel. One of the questions on the questionnaire stuck to mind. The question was "How would you feel if someone greeted you (say a fellow passenger) when you got on the train?" There were several options including you'd think it was strange and it would make your day. I choose I'd think it was strange because that was the first thing that came to mind.
As I was on my way home I pondered upon the question. Is it so strange for people to say hi on the train? Is society so insular such that we don't interact with people we don't know? Has the growth of the ipod and other mp3 players lead to the demise of social interaction? Do we prefer to go online and talk to people rather than do it in person?
I looked around the train and no one was smiling. Were we all so fed up we've also lost the art of smiling? Just then the annoucement came over the loud speaker "We are sorry but the train has developed a fault and will be terminating at the next stop". Now that wiped the smile off my face...