Although I'm realtively young, I do feel that there is a huge change (not for the better) in parenting trends. I see the parenting trend as "I want to be your friend, not your Mom."
I see this all over the place. At the grocery store, the kid is running rampant, knocking things over, screaming for his mom to buy him something, and his mom says, "Honey, don't climb on the shelves, OK? Don't open that box of cereal, OK? We can't buy that toy, OK?" Do you see the trend? It's that "OK", meaning, if it's OK with you, I'd like to say no to you; may I have your permission to discipline you?
The parents want to befriend their children and don't want to be the 'bad guy' and say no. So the kids basically rule the roost, but they don't have the intellectual or emotional capacity to really be their own disciplinarians. They lose trust in their parents and also lose respect for them too. That's when kids start telling their parents to 'shut the f**k up' (yes, I heard a 15 year old tell his mom this in the office where I work; I bolted a glance at her, expecting her to stand up for herself as the mom and as a human being. She just simply clamped her mouth shut-exactly as ordered.)
Sometimes a firm (not with all your strength) swat on the butt is necessary to snap the child back to reality. A quick swat is used to get their attention. When a child is completely out of control, yelling or "reasoning" with them is like talking to a tornado. As sweetstuff said, spanking is only one small part of discipline. Spanking alone, without ever speaking to the child explaining the problem, does absolutely no good. It has to be used appropriately.