Throw me into the spanking camp...
No. Wait. that sounds really wrong....
Umm... Let's start over, shall we?
I'm firmly of the belief that each child is different, and that there is no one size fits all rule (spanking good vs. spanking bad) that can ever adequately deal with this concept we call child rearing.
I'll use myself as an example. I was spanked as a child. Both in a loving manner, and in an abusive manner. Yes, I was old enough to know the difference. My parents were very loving in their discipline. I *knew* that they hated having to spank me. But they also knew that I was entirely too "strong-willed" (i.e. stubborn) to listen to them most of the time. And my brother? He was the poster boy for the stubborn kid. Boy, do I have stories. And yeah, he got spankings more frequently than I did. But he also knew that Mom and Dad loved him. Now my grandfather used spankings as a means of physical abuse. Little clues like, "you're gonna keep getting spanked until you quit crying!" As a (for the most part) well-adjusted adult, let me tell you what the results were: I love my parents, very dearly. They Raised Me Right. My grandfather, on the very rare occasions that I see him, I'm as likely to punch his lights out as shake his hands. I don't go out and kill innocent animals, or innocent children. I know my parents didn't abuse me by spanking me. I *DO* know my grandfather abused me by spanking me.
Now, for a counter-example, my wife. She was never spanked as a child. Yet she also turned out to be a very well adjusted adult (other than marrying me, that is, but that's also a whole different thread). Her parents learned very early on that she was one of those very sensitive kids, that a stern word was all the correction she ever needed. Even as a 3 or 4 year old, all she needed was a stern word. She never got into any trouble as a young woman, and is today a very good person. Her parents also Raised Her Right.
So, here's where I step off the soapbox. There's no one-size-fits-all rule. Spanking can be a very effective tool in child rearing, one that should *NOT* be excluded from a parent's toolbox. But it all depends on the child. Some kids will need a spanking. Others, won't. It's part of a parents job to figure out what kind of discipline an individual child needs.