Groupon headquarters in Chicago.
Andrew Mason, founder and CEO of Groupon.
4-17-09 Groupon Chicago. 600 West Chicago Avenue. Chicago, Illinois. Shopping story on this new Web site, Andrew Mason, offers a huge coupon or "groupon" every day and everything from beauty treatments to sporting events. Photo by Scott Stewart/Sun-Times
In this Sept. 22, 2011 file photo, employees at Groupon pose in silhouette with the company logo in the lobby of the online coupon company's Chicago offices. | AP file
Groupon turned down close to a $6 billion dollar buyout offer from Google in 2010.
Groupon CEO Andrew Mason | Tom Cruze~Sun-Times