Well, I won't be a parent until April, but I'll answer anyway (I was a kid once...)
When I was a kid, my sister and I would get spanked if we did something that my parents considered bad enough. It was not a beating, there were no belts or sticks, and it did not happen everytime we got into some form of trouble. From my standpoint, I knew that it hurt a bit to get spanked, and that was enough to stick in my mind and make me think twice about getting in trouble sometimes. A spanking got the point across.
I believe that a spanking is fine, if necessary, to teach a young child about actions and consequences. When I was older and could understand it, my parents stopped spanking and would do something else (grounded, loss of privledge, etc.) and also explain why we were being punished. However, when a kid is too young to be reasoned with, a spanking works as a consequence that they will understand.
I do not believe in beating or hurting a child, and this is where the problem is. My parents didn't do that to us, but unfortunately a lot of parents do. You have to know where to draw the line. It's a personal responsibility that can't be governed, standardized, or monitored. You need to know, as a parent (and I believe that anyone with common sense would), where the line is- when does it stop being a spanking and start slipping into a beating?
The bottom line for me is that I don't want anyone telling me what I can and can't do with my child regarding discipline. If I decided to use spankings, I know that I am not the type of person who would cross the line and wind up losing it and beating my kid.
Outside of the home, however, like at school, kids should never be spanked or punished physically. I don't think that anyone but a parent has the right to decide on or give out that type of punishment.
One final point- our society is really getting soft, and this is a great example. All of these people who are shielding their kids from things such as losing a game, failing a test, or getting punished when they deserve it are creating a bunch of monsters. Two of the biggest problems we have in society now are a sense of entitlement for whatever you want (without working for it), and a complete lack of responsibility for your actions. Keeping kids from experiencing hard work, responsibility, discipline, and failure will only make these problems worse in the future.