File photo of Groupon CEO Mason preparing for the opening bell ceremony celebrating his company's IPO at the Nasdaq Market in New York

 
File photo of Groupon CEO Mason preparing for the opening bell ceremony celebrating his company
Groupon Chief Executive Andrew Mason (L) prepares for the opening bell ceremony celebrating his company's IPO at the Nasdaq Market in New York in this November 4, 2011, file photo. REUTERS/Brendan McDermid/Files