Yeah, people will naturally pause while talking to you in the car if you changing lanes, making a turn, or something else where they can tell requires some concentration. People on the cell phone will keep talking away not knowing what you're doing right then. That's why blue tooth headsets cause as many accidents as just holding up the phone. It's the loss of concentration and the unaware person on the other end.
To really prevent accidents, we're going to have to ban all cell phone use by the driver in the car and I think at that point, they would be too much of a public backlash.