If you're calling bubble and confused about how they're running at a loss don't miss this line:
"Participating Merchants: 56,781 in the first quarter of 2011, up from 212 in the second quarter of 2009"
That database of 56,781 merchants is GOLD.
The way their sale staff works is to create direct relationships, phone contact etc - that is not a cheap proposition.
In terms of growth potential there are 10x as many restaurants in the USA as Groupon's entire universe of merchants today.
If they continue to capture the consumer mind that they're the best in the world to answer those two questions, their valuation and growth potential is insane.
Refs:
http://answers.ask.com/Food_and_Drinks/Restaurants/how_many_...