I am going to disagree with the majority here and say I don't believe in spanking children. You can't teach a child on one hand not to solve their problems physically and then punish them by spanking. I have years of experience as a nanny, and I can tell you that the most effective punishment I have ever used is to take them to a quiet corner and have them sit there, one min for every year old they are, and if they get up before time out is over, the time starts over.

yes, everyone needs a whack now and then
this coming from a kid.

it's okay somtimes, it's better for a time out or no toys or lights out and bed earlier or no desert but yes, its fine.

Yes of course! Don't be abusive, but when they do something worthy a slap on the bottom is a reminder that it's not okay. Not until this past few decades has there ever been a problem with it.