The answer is: there is NO reason (other than assuming maybe that someone else will buy it from you at a higher price).
Look at "similar" companies that act like a middle man between the consumer and a business (like travelzoo, price line, even ebay). They trade at ~2-5 revenue (which is still very high), AND grpn has no profit... This thing is heading toward a single digit, and later to chapter 11.
I am not talking about the immediate term, but financially they can NOT be a $12B company. It just can't be. Maybe they will touch the 30s and 40s too (and this gives the gamblers a sand box to play) - but final stop is single digit.