I must admit, being the mother of an only child, I never thought of outsourcing his toilet training to another, older child using jelly beans as payment. There's an economist who swears it works, if you handle things correctly. (Beware the budding entrepreneur who force feeds his young subject water to grow his business.)
I've just had a ball reading the most intriguing little blog called "gametheorist" by Joshua Gans of Australia, author of a forthcoming book called "Parentonomics." It is, essentially, the economics of parenting.
If you want to elevate the spanking argument onto a whole other level, he's your guy. He and his guest economist-parent bloggers also write about the economics of the tooth fairy, why parents should pretend to have superpowers, why it makes sense to teach children subtraction before addition, why shared birthday parties save money and how to compute which incentives get the best results with kids. When they write about thumbsuckers, they are being literal.
Now this is some great dinner table conversation.
I believe a little spanking is ok, just never when you are either really tired or angry, as it is a fine line that can be crossed and never telling the child they are going to get a spanking when the other parent gets home or by the other parent, The child has to be able to associate the wrong with the reason they are getting a spanking.