Talking on the phone in public - it's become ubiquitous. Everybody does it, everywhere. When did we decide that it was okay to inflict our conversations on everybody else? And when will people decide that they don't want others to hear their conversations?
In the last week, I've heard people cussing each other out on the phone, arranging medical care, arranging social gatherings, and just catching up with each other - all on cellphones, on the streetcar. I have to admit, I have done it too - I get phone calls and talk, not paying attention to what's going on around me, who is listening, who is trying not to listen. It's a different social dynamic now, and I'm sure that it's going to keep changing.
I'm a quiet phone-speaker and hate answering a cell phone (I don't even have voice mail on my cell). I am very self-conscious of people listening to me. :D And I am very aware of people on their phones - on the GO train. Some people are extra loud... like they are talking to you, so you have to look up only to realize they are just sharing their conversation with the whole car.