No spanking under 18, I say.

Seriously, it's entirely possible to raise a child without hitting them anywhere. I was never hit, and while no saint, I've never stolen, plundered, pillaged, cheated on my taxes, assaulted anyone or otherwise was lawless. I also worked with kids for many years, and besides that we weren't legally permitted to hit them, none of us would have ever considered doing so, and we were still able to maintain discipline.