I actually think using phones and smoking/eating etc are all dangerous at the wheel. Even when using a bluetooth headset with the phone.
I know sometimes work have phoned me whilst i've been on the motorway and asked me something like where a file is on a shared drive and i've had to think it through, and my mind has not been on the road. Maybe thats just me
Well it's me too. So far, while on hands-free, I've...
Been on an unfamiliar roundabout and had no idea which exit I was supposed to be taking.
Driven too fast past a speed camera and had it flash (fortunately no ticket followed)
Nearly missed my exit from the M6 onto the M56.
Fortunately I've never had a near miss though.
Phone calls can be a distraction, hands-free or not, though it depends on the kind of call. If the person at the other end is demanding a lot of concentration (expecting you to solve a problem or remember something from ages ago) then it's a lot worse than if a friend is just ringing up to see how you are.
The problem is that if they ban using mobiles while driving altogether, people will just break the law. What's more, they'll have no incentive to use hands-free because it'll be just as illegal as holding the handset to your ear.
A hands-free kit is safer than a handheld mobile, so the status quo is about the best we can expect.