This tweet from Thomas Purves, who describes himself as both an "Impatient futurist" and "agent of change," seems to be both heartening and disturbing. Here, presumably, is a taxi driver who's decided not to let the wave of technology just wash him away, and has instead dived in with every car-summoning app available. Good for him.

And yet, just as presumably, we have a driver who's now looking at five phones, which is about five more than anyone should be looking at when they're trying to drive and not, like, kill people.

Which brings us to the question posed in our headline. How many dash-mounted phones is too many for a driver on our streets? None? Two? Ten? What's the most you've seen in concurrent action?