Update: A Nudge in the wrong direction

LibertyCat says he would have focused more on why Nudge wouldn't work. Tim Harford, for example, argue that people aren't always that easy to Nudge. Nudging only works if people have to make an important decision once or if the decision has a low cost (financial or otherwise). If someone makes an expensive decision numerous times, they learn from the experience and begin making increasingly rational choices.

So why are people obese? Well, perhaps being moderately overweight doesn't have many costs. If you are accepted by your partner and peers, and won't suffer unduly until you are in late middle age, then an extra chocolate bar looks like a rational decision. Many people don't care much about the cost to their health because they reason it's better to drop dead at fifty with a heart attack than get Alzheimers' at ninety. I can't say that's the wrong thing for them to think, although public health experts would disagree.

Another reason why Nudging doesn't work is drafting the legislation. Can you imagine drawing up rules to prevent shops strategically locating chocolate oranges? If the idea brings you out in a cold sweat, you wouldn't be alone.

Finally, to reiterate my point, widespread Nudging changes the relationship between the individual and the state. The Government no longer exists at the behest of the people because Nudging assumes they are irrational and cannot be trusted to act in their best interests.

Or, as LibertyCat put it, if democracy only gives you the choice about whether the state should be your father or your mother, then we're screwed.