You'd think it was a no-brainer. The roads are full of such morons. They drift out of their lanes on the highway. Don't signal when changing lanes because their one free hand is 'busy' doing something else. Often they're going 10 miles or so below the speed limit while 'chatting' on the phone. The police really need to crack down harder on this. It's an extremely dangerous thing to do.
The crux of the issue is not the cell phones, per se, but rather those that drive badly while on them (and many that drive badly while not on them). The Police used to respond to poor driving, and not be seat-belt/cell phone nanny staters.
Enforce the driving rules, IMO.