When King Digital made its stock market debut in March 2014, the popularity of "Candy Crush Saga" popularity had peaked, and so had the London-based company's sales, making for a dire opening day's trading on Wall Street. The shares fell from $22.50 to around $18. Coincidentally, $18 per share is the price that Activision Blizzard, a giant of more traditional console and PC video games such as "Call of Duty" and "World of Warcraft," has agreed to pay to end King's brief and bumpy stay on the public market.