I think it is important to explain that the "touch with the back of your hand to see if it is live" advice should be taken in-context.

It is not a general-purpose method for testing if a circuit is live. It is just a good habit that MIGHT save you when you go to purposely touch something that is disconnected, turned off, verified with a meter or test light and SHOULD be perfectly safe to touch. As long as you intend to touch it anyway, make your first touch with the back of your hand.

Please don't use it to find out which breaker controls a circuit by having your wife in the basement turn off one at a time while you repeatedly touch the bare wire with the back of your hand.