On Christmas Eve, Chuck Wendig posted a long rant to his blog with the title "Spanking Your Children Is Hitting Your Children". Amid his usual profanity, he put forward the opinion that spanking your children is a form of abuse, which is not a new argument, but was backed up with some reasonable and well-thought-out logic.
His follow-up post attempted to address some of the comments he received, and he presents studies that support him, though none that found any alternative conclusions. The main thrust of the argument here is that spanking is the low-brow, knee-jerk reaction to tantrums and other behavioural problems in children. It only teaches them to fear you and that they should not behave that way, not why they should not.
Here's where I started thinking that, whether you spank or put your child in time-out, neither approach is going to accomplish any understanding without some long discussions where you outline expectations and that actions have consequences, choices and all that kind of thing to your tantrum-throwing two-year-old. Do they understand? Probably not. There is going to be a time in your child's life when they are punished for something and cannot know why.
Mokalus of Borg
PS - I don't have kids, though, so I'm not actually qualified to weigh in on this.
PPS - You'll note that hasn't stopped me, but feel free to ignore me on that basis.