Wow, a lot got said on this thread while I was busy elsewhere today! Lots of things I want to comment on, but I'm going to start with this:

Connie, you say you were a very strong willed child, and were unaffected by such things as time outs, and you refused to obey authority until you were spanked. You also say you were never beaten up, and it never left a bruise.

I'm glad it worked out ok for you. And I don't think there is anything wrong with a spanking that doesn't leave a bruise, in and of itself. Some things work for some kids, and other things work for others. So I think the most important thing is to figure out what works for your kid. And it sounds like your parents figured it out with you.

With exceptionally difficult children, any sort of punishment often turns into something that resembles the nuclear arms race... it just keeps escalating. So when taking away one toy doesn't work, you take away more and more until they have nothing but a mattress in their room. When a brief time out doesn't work, it gets longer until they are grounded for 4 months.

The problem with spankings or other physical punishments, such as another old favorite, going to bed without dinner, is where do you go from there when they don't work? If the only tool a parent has is to resort to this sort of stuff, then what about the even stronger willed child who is not affected by a spanking any more than you were by time outs? Do you hit them hard enough to bruise? If/when that doesn't work, do you hit them hard enough to break bones? If missing one meal doesn't bring them in line, do you withhold food for a whole day? a week?

McKinsey and a few others have mentioned things such as chores and other physical labor as an alternative to spankings. This will often work with children who don't respond to time outs/grounding or just being talked to. It still reaches that physical discomfort spot that seems to need to be pushed on some kids. The example of having to walk to school when kicked off the school bus is another great one. Exercise can also push that button. Physical punishments, which do work very well with some kids, do not have to be spankings.