Depends on quite a few factors. The parents, family, guardians involved, their children, their environment, resources, who their child interacts with, their friends, whether they live in the city or country, how old the children are.
Lots of posters have given personal accounts on whether they were physically disciplined or not, which is a reasonable frame of reference, but its worth considering that usually another large factor involved here as far as the administering of physical punishment or lack of is whether one is in an environment where others are treated the same way. Physical punishment as far as parents and teachers was a lot more common and accepted in many places in the past, and so psychologically many children weren't as vulnerable to overly negative affects as say situations where some children were punished physically, but others weren't. This would lead to complications where you had parents who were physically disciplined alongside family members and friends at school, believing it would therefore be okay to physically discipline their children the same way because they turned out okay, not taking into account that their children may interact with many more children who wouldn't get physically disciplined leading to confusion and resentment that stayed with the child longer than any physical effects. Generationally there are many more parents today who can raise their children differently and in ways other parents and children can be and are aware of as opposed to previous generations prior to widespread internet access, even reality TV to some extent. In many ways its harder for a parent these days to be good parents. A lot more pressures and risks to their children.
If you have a single parent who works and they have a child who may demonstrate short bursts of hyperactivity and they live in the city and a quick slap on the hand is enough to get their child to focus and pay attention and associate negative consequences to certain behavior that may otherwise endanger them (hitting other children or elderly relatives) coupled with that parents patience and explanation towards the child as far as what they were doing as wrong and why they were hit on the hand and that the parent still loves them and that they should always be honest and so on, I see nothing wrong with that personally. Its really just that the parent should always be in control and their actions should always be well considered and not based off quick emotional reactions or stress or pressure. Not a good idea to hit children without them understanding why or if they are aware of their friends and friends parents whose teaching methods might be superior and or less severe in the eyes of the child. Its that perception that is what can mess with a child psychologically.
So short version is that there are too many alternatives for a parent, the past or personal experience is not a good reference for parenting success and thats okay, since all parents should want to be better than their own parents even if they had great parents, and ideally, ideally parents have the time, resources, and support to actually be a good parent. As in teaching a hyperactive three year old to always hold the parents hand when crossing streets and to never run away and run on a road, a possible scenario where a busy or stressed parent may be excusable for using a smack on the hand if or when a child attempts to run out on a road or so on. Just again thats not a situation a parent would want, much more ideal to teach them road safety well in advance.
Personally I wouldn't use physical discipline nor did I in raising my baby sister, I was lucky to read some good books on parenting and have resources and time to pursue superior alternatives.