Andrew Mason, chief executive officer of Groupon, Chicago's Internet deal maker, said he would no longer lead the company he founded. "After four and a half wonderful years as CEO of Groupon, I've decided that I'd like to spend more time with my family," he wrote in a quirky letter to colleagues. "Just kidding," the letter continues, "I was fired today." The Chicago Tribune reported Friday that Mason's departure had been expected. Apparently, his fate was sealed when Groupon released disappointing fourth-quarter results that showed the company was still struggling. For a while, Groupon, which is not yet 5-years-old, enjoyed a meteoric rise as a high-tech success story. It went from a start-up to the employer of 10,000 workers. But Groupon's downturn has been equally fast. Google offered $6 billion to buy the company in 2010 and Groupon turned down the offer; now the company is worth about $3 billion on the stock market. "It's extraordinarily difficult to grow a company as fast as they did and get it all right the first time. The change in leadership will give them a chance to back away from that criticism a little bit and try to keep growing the company," Matt Moog, a Chicago tech entrepreneur, told the Tribune.