I have to say I agree with Bloss.
It's not something that is yet a "live" issue for me. My ds is only just one year old and so far has been the "child from heaven" so smacking is not something that has ever come up. However, I may well in future "smack" (eg smart rap on the hand) him in extreme and dangerous circumstances, to get across a message strongly, quickly and memorably, especially while he is too young to reason with. The fingers in the plug scenario is the obvious one.
I had an interesting chat with muy mum about it this weekend. We joked about about how they were "awful" parents because they smacked us ("normal" behaviour in the 60s). I know I was smacked on rare occasions - but can't actually remember any of them. I can however remember being threatened with having my mouth washed out with soap if we swore or fought with each other - and I think it even happened once (ugh!). Now that used to give us pause for thought! My brother and I both still have a close and loving relationship with both our parents.
My mum made the interesting point that babies before they can communicate are more like young animals - and in the animal kingdom, if the young do something wrong, they get swiped by the adults - and soon learn (think lioness and boisterous cubs). Nature is cruel - and the alternatives if they don't learn fast are not pleasant.
Now I am not suggesting that our children are animals - but it is an interesting analogy.
And before opprobrium is heaped upon my mother, as a teacher, she always refused to use any form of corporal punishment, yet was apparently highly liked and respected by her pupils (even mentioned once by a famous pop star as his favourite teacher!). Her view was the the belt was far too "quick" a punishment (and hence prefered by the culprits as it was over and done with) and also too often reflected in the violence of the problem kids' home environment. She would give punishment homework or detention - something that took up time and made them think about what they had done.