a smack on the butt's not a horrible thing as long as it's a simple smack on the butt. it's the fact that you were angry enough to resort to that which wises a kid up, not the "pain" inflicted. hell i don't remember ever getting a spankin that actually hurt. it was the fact that i did something that bad that mom/dad would be this upset.
and a spankin has to be a very seldom thing, because a smackin on the toosh that's done correctly is actually very easy for a kid to get past and say "that doesn't bother me".

the majority of the time, i was put in my room. but i had plenty of spankings and it never made me "prone to violence, bla bla". pain happens and a kid knows her parents still love her. there's a line between discipline and abuse that people have stepped on so much that it's faded and hazy.