alipsa,

A simple disconnect of the negative battery terminal is MORE than enough to prevent discharge of the airbags.

It's also the main precaution when doing any wiring work.

When you are changing a dash illumination bulb, you will be unplugging things, so it's better to have all power disconnected.

By disconnecting the ground wire from the battery, you are leaving no return path to the battery to complete a circuit. Even if a hot wire fell across a bare metal surface (not likely in a new car) it would not be able to complete the circuit.

The warning was not meant to make you afraid... it was meant to inform you.