I don't have a problem with smacking to teach discipline, but having said that, it should never be done in anger, it should be an absolute last resort and there is definitely a difference between smacking to startle the child and abuse. I have only smacked my daughter twice and it did work but this was only after trying every other possible tool I could think of and we remained calm throughout it. I was smacked as a child and have no emotional/physical side effects..and in all honesty as we got older we didn't get smacked because we just knew when we had gone too far. So although I don't have a problem with smacking for discipline..it needs to be an absolute last resort and should definitely not cause injury (it also needs to be done in context..don't smack for everything you don't want them to do, only very serious things otherwise it won't work and could possible teach them it's ok to hit). Discipline is one of the hardest challenges a parent faces!
ITA. I have smacked before. Especially Chase who likes to do stupid things like burn his hands on the oven and end up in emergency, pull the oil heater on himself, run into the middle of the bus mall and almost get hit by a bus on the kurb. In those situations he has got a smack because I can not risk him doing them again (well not the burning himself thing but when he went to touch hot again I smacked and said no HOT)
However these occasions are rare, not daily or weekly or even monthly. I can't remember the last time I smacked.
We use the corner here with great effect. Even when we are out, if they are naughty they get a warning that if they don't stop it will be the corner and usually we don't get to that stage. However, if we do, they go face a wall or corner somewhere. Believe it or not we don't get ANY remarks from passers by as you would if you smacked.

When she came to the room with the wooden spoon she would ask me why I was getting the smack and I would tell her. Then I had to bend over and she would give me a firm smack on the bottom with the spoon and tell me not to do it again! I can't see anything wrong with that?!?!? It is the smack out in public to humiliate the child and the passing whack or grab that is abusive and destructive because you are instilling fear into your child. Also if you use your hand instead of an object your child will associate you with the pain, that is why you have to use an object like a wooden spoon, so that they know that if they do something wrong that spoon is going to smack them on the bottom and it is going to hurt. I can guarantee you that it stopped me from doing naughty things when I was a child.

Firstly sounds like you stopped your behaviour out of fear of getting a smack, not because you knew the behaviour was bad. I think it is cruel to tell them when they get home they will get a smack. It is making them spend the whole time out worrying about what will happen when they get home. I know this because I have had many discussions with my mum who was always told "when your father gets home he will deal with you" and she would worry ALL day. (usually for no reason because he would either say not to worry or yell a bit)
Secondly it is illegal to smack a child with anything OTHER than your hand, so a object SHOULDN'T be used. You are only allowed to smack below the waist and you are not allowed to leave any marks.