I think it's unnecessary & introduces violence as an acceptable way to solve problems. My son went through a short phase of hitting my wife & I think it was initiated by a few smacks that I dished out to him. I regret taking that path.

I think what's more important when setting boundaries, is that you persist with them. Your voice is far more useful in this. Your children crave stability as well as your approval & attention but you cannot withhold something that you've not already given them.

It's important to remember that kids learn by observing. Lashing out with anger & violence when things don't go your way shows them that this is how you deal with the undesirable.

I think it's sad that our elders aren't as involved with child rearing any more. You're biologically geared to have children young but mentally unprepared to impart wisdom (I wasn't anyway).