This decade's greatest Internet hits — Google and PayPal — make so much money because they help money change hands more efficiently. The next great wave of moneymakers on the Web won't be nearly so utilitarian, Keith Rabois, VP at widgetmaker Slide, argues in a guest post to AllThingsD. Rabois says the Web's next mint will be made on fun — a very underrated commodity, he says. To demonstrate his point, he harkens back to the week of April 21 and the electoral contest that captured all of America's attention. Not the Pennsylvania Democratic primary, Rabois writes. "I'm talking about American Idol." Then he lays down some convincing numbers: