For a melancholy example of the power of celebrity, head to the Alps. Since Michael Schumacher’s accident last December in Méribel, the use of ski helmets has soared in the mountains. My skiing instructor in Verbier, in the Swiss Alps, said the Schumacher effect was particularly acute among the young and the old — it’s seasoned skiers in their forties and fifties, battling the neurotic caution of middle age, who still keep their heads bare.