Famed as a hotbed of debate over academic freedom, New York's most elite school is also a playpen for sexual hijinks, sophomoric antics and the wacky indulgences of the children of the rich. While their parents shell out $33,246 a year in tuition, Columbia University students doff their clothes at naked parties, flock to sex toys workshops, broadcast porn on campus TV, bake anatomically correct pies for the "Erotic Cake-Baking Contest" and heat up the steps of the Low Library in a mass makeout session called the "Big Kiss." And of course, there's always the stimulating game, "Guess the Number...