Actually,
I'd never thought of the metal bit hitting a live cable with one of these drills, although metal appliances have always required an earth (ground) wire in them here.
I owned a Wolf drill that had a metal case on it for a few years, and as KJ said above, these drills don't stop for anything, thankfully my drill never had one of them trigger lock things that most drills seem to have on them these days. I think if it got out of control on you, all you could do is run away from the thing and possibly turn it's power off somewhere.
