The tube is already unpleasant enough for those of us who have no option but to use it.
If they could make it that voice was banned on the tube, and only texting + data allowed , then I'd be all for it. However if you've got Skype-like-service and broadband data, the voice restriction could be a bit pointless .
What with people treading on my feet, bashing me with ruck sacks which they seem to want to keep on their backs at all times, even on packed trains, gassing me with smelly armpits, and ting tinging me out with their crap in-ear headphones attached to music-player of some description, well the thought of having some idiot screaming down their phone, saying at 120 decibels " I'M ON THE TUBE" in their best Dom Joly voice just feels me with dread, fear and anger.
Please , NEVER allow voice calls on the tube.