I think it's too simplistic to try to draw a direct cause-effect link between smacking (or lack there of) with the behaviour of teenagers today. There are too many social issues that at play here to suggest that you can stop your child from certain behaviour if you smack them as children.
Sushee I totally agree. I think children are far more influenced by our values and world view as parents, than one or two individual behaviours. I think too often we put the behaviour modification (ie the smack, the time out, the cause and effect discussion) into practice before we actually think about what values our children need in order to make a behaviour choice.

Perhaps if we start with the big picture, the values, and then work in towards the small picture, the behaviour modification, we'd have more success Afterall, behaviour is only the outward expression of what we feel, think and sense.