I was taught from my driving instructor (who drove trucks for a living) to drive with two feet. As long as you're driving automatics, it only made sense that this provides safer driving since:
1) You can't hit the wrong pedal with the "one foot" you're using. Left foot is always brake, right is always gas.
2) You can cover the brake while holding the accelerator down. Not needing to depress and switch pedals improves reaction times.
3) If you ever did slam down with two feet, brakes override the engine. As a two-foot driver, I doubt I'd press the right foot down to brake, though -- I've had enough close calls. Additionally, I've occasionally tried using my right foot to brake in low-speed situations and it's scary, since I'm so hard-wired to only use the left.
I don't recommend re-teaching existing drivers, but we should at least be teaching new drivers the safest way.
The "one foot" style of driving is simply a poor carryover from manual transmissions. If automatic-transmission cars were designed from scratch today with no backstory, we'd have the brake over on the left, the gas on the right. Simple, obvious.