You have to understand that any disciplinary action has the potential to become abuse if mishandled. I believe that a spanking can be a good disciplinary tool, but only when done as a last resort, when you're confident that nothing else will work, and not when the parent is angry.
It's so easy to misuse a spanking, simply because it's such a seemingly good method of discipline. It's scary to any child, it can be done in minutes with little inconvenience to the parent, and the threat of it can make most kids change their attitude really quick. But if a parent relies too much on it, than their authority becomes based in fear, not love or respect. Such an environment screws up most children, because they learn that the parent is right because he is stronger, not because he's actually right. And the second the child stops fearing the parent, all of the things the parent has tried to teach their child disappears with that fear.
Wait, who am I responding to now? I feel like I just typed up a two-paragraph response to the wrong person...