It's a toughie. There are a lot of bad parents out there, so laws that prevent kids from actual mistreatment are pretty necessary. I think we used to trust parents not to murder their own kids in the swimming pool, or sexually assault them. For some reason, parents as a group have lost this trust and now every little thing parents do is up for scrutiny.
I spank my kids when they deserve it. Let me rephrase that- I spank my kids when it's for their good and not when it's just for my own. At least, that's my intention. I'm sure many of you wouldn't condone this.
I think my kids are pretty good. By that I mean they are (mostly) well behaved and are concerned for the wellfare of others. They are kids, so they act up from time to time. But they know what my wife's and my expectations of them are- what the rules of the house are- and what the consequences are. Seems to be working pretty well.
(For referrence, my kids are B8, G6, G4, B2)