wasn't the statistic that blah percent of people said they felt parents should be allowed to smack their children but only 10% (?) said they smacked theirs?
It takes at least a generation to change child care practices and my generation (40's) were all smacked (not often in my case) and it's difficult to see why it's a problem if you felt it wasn't a problem for you personally. I think as an acceptable practice it will die out slowly over the next 10 years as it becomes more socially unacceptable.
I don't think it is that socially unacceptable to smack at the moment - by that I mean a small smack not a good lamping and I think people still distinguoish between the two.
I suspect there is also an element of backlash against constantly being told what to do - "I'll raise my children how I want to thank you very much", resulting in parents who wouldn't actually smack their children saying they think its OK to. More of a vote against the nanny-state than anything else.
Entirely conjecture on my part though.