If you watched some NFL football over the weekend, you were probably inundated with ads for DraftKings and FanDuel. Each spent over an estimated $10 million on TV advertising in the first week of September, and DraftKings reportedly spent $20 million on ads that ran 5,800 times over the past week. DraftKings and FanDuel are the two biggest companies in daily fantasy sports, the hyperactive cousin of fantasy football that insiders refer to as "DFS." It's become incredibly popular. Some people risk $5, others more than $100,000. But it is so much harder to win big than most people think. ... (full story)