I'm guilty of this.
Scenario: I am on my way to point A, or I have to wait above ground for a metro and I have a few minutes. I call a family member or a friend to pass the time. We talk for a few minutes and then I rush off of the phone because I am on my way to my destination.
I am on my way to point A, and someone else is on her way to point B. She calls me, and rather than let the call go to voice mail, I pick up the phone and we both talk until someone has to get off of the phone.
Someone is on his way somewhere and he calls me. He talks until he has to go and jumps off of the phone. I don't get to say what I wanted to say, and neither does he, I suppose.
I am on a date or out with a friend and he or she gets a phone call. He or she picks up the phone; perhaps he or she doesn't talk for a long time, but it nevertheless interrupts whatever is going on. I have done the same thing, but I usually say "excuse me, I should take this." Some people don't. Or there's the missed call with the voice mail beeping and the "excuse me, but I have to check this and call the person back" (and interrupt whatever is going on).
And I pick up a phone call, rather than ignore it to get even.
This is not a revelation, but mobile phones completely change how I (and everyone else) interact with other people.
And most times, it sucks.
**I know that I am not guilty of talking too loud on public transportation, out on the street or in a restaurant.