I was spanked rarely as a child, most of the time, nothing more than a swat, once was like 6 when i almost burned down a storage shed (i was a pyro as a kid). I don't think it was 'necessary' to get a point across to me, as i was generally a kid who hated being in trouble. i still do, actually, so i was pretty much just one of those 'good' kids that didn't do too much to get into trouble. I was also one of those kids that you could say 'no' to and i'd listen for the most part.
On the other hand, i pretty much knew that they weren't bluffing when they said i would get in trouble and i knew what it would lead to, so that may have shaped my fragile little mind as well, but i dont' think so. I just think i like making people happy more than i like doing whatever.
on the 5th hand, i am also a bit of a strange person and nothing that applies to me applies the same to anybody.
Do i think i would spank as a parent....I think so as it is an immediate 'attention getter' but i dont' think i'd go overboard and it certainly would not be my first option. I hate causing pain or fear.
Now, would i spank my gf..oh hell yea
(sorry, had to throw in some levity as i have known too many abused children along wtih a lot of children who were properly spanked when appropriate)