Well, it depends. I would never, ever hurt my kids, but sometimes whenever they won't obey you, then you have to spank them. Not hard, but enough to get the point across that you're serious. Trust me - If you only yell at your kids, or do something that doesn't really get their attention, and make them feel like they're not being punished, then that will get old very quick.
My cousin does that with her children. Whenever they are doing something wrong, she's like, 'No honey, don't do that!', and you know what? The child does the exact opposite. Her 3 year old daughter is honestly a terror to be around. She won't listen to you, she talks back, and all of that stuff, and it's because she hasn't been disciplined.
My mother has spanked my brother and I before, and I'm actually glad that she did. It taught us who was boss, and I don't disrespect her at all. She did a good job teaching us manners and everything, and she didn't go overboard with it. She never abused us, she only spanked us whenever we deserved it, and it wasn't so bad. Sure, I didn't like it, but I'm still alive, and I love my mother. She's the nicest and most caring mom that anyone could have.
I have some more stories to back this up too, if anyone wants to read them, lol. =P