The IPO of King Digital, maker of the popular video game Candy Crush Saga, soured on its first day of trading. Its stock dropped $3.50 or over 15%, to close at $19 per share. Investors were likely concerned about the faddishness of competing games such as Zynga's Farmville and Angry Birds, both of which have lost their once dominant positions. Yet the company generated well over $500 million in profit in 2013. And it has paid its two private equity backers nearly $300 million in dividends.