My husband and I were walking through a park when we passed a man lying on a hillside watching a baseball game.
The man said, “Hey, can you do me a favor?”
How odd, to request a favor of two strangers walking past! My immediate thought was perhaps that he was hurt, his back was out and he couldn’t get up, and he needed help.
We both stopped and looked expectantly at him.
He noticed us staring, mouthed, “Sorry!” and showed us the tiny cell phone he was using.
It wasn’t rude, just weird. 
Knee-jerk moderate that I am, I figure that there’s a certain cell-phone etiquette and as a society we’ll eventually shake out a consensus on what that is. I think it’s almost universally agreed that some cell behaviours are unacceptable, but others are on the borderline.
I find it unpleasant to have to listen someone conversing on a cell phone in public, even when they are not speaking loudly, but I can’t put my finger on why it’s more annoying than two people talking. I guess that I’ll get used to it with time, particularly if I get a cell phone myself.
However, I cannot abide getting a dirty look from a cell phone user because my conversation with an actual person standing physically next to me is interfering with their phone call. If you’re in your living room and a call comes in, on your cell or your landline, you’re perfectly within your rights to ask the people in the room to please be quiet while you pursue your telephone conversation. If you are in public you have no right to expect others to lower their tones because you’re on the phone. You can take your portable phone and go find a quiet place to talk where you are neither inconvenienced by, nor inconveniencing, anyone else.