Hell yes! I almost got hit head-on today by some poser making a right turn while cradling his cellphone. He couldn't keep both hands on the wheel, so he tried the 'palm-the-wheel' method of making a turn - unsuccessfully. His 'grip' slipped and he came about 70% into my lane. Of course, he then drops the phone (almost out the window, but no such luck) and quickly over-corrects his car into the curb for a few yards.
I bought a BlueAnt in-ear Headset for my phone a year or so ago and I never get in my car without it. I think it cost me a whole $30. Hmm, $30 for a headset one time or $300 to replace your rim & tire (or a LOT more if you wreck) because you cant react in time?