well I was lucky enough to witness this. Not only once but more than twice:
A luxury sedan was driving erratically in front of me and I didn't know why. When we came abreast, indeed the driver was talking on his phone.... but wait .... he is using a hands-free gadget!
So why is he still driving erratically while using a hands free phone?
Because he was gesturing with both his hands as if whoever he was talking to on the phone could see his hands and he using his elbows to steer.
Mind you I've seen this on different occassions. With the way they are driving, speaker phones are no use. Good luck to all of us!