Outside of valuation issues, investors need to determine if Groupon's business model is sustainable over the long term. Groupon holds no patents, so does it offer a service to consumers with enough differentiation and value over others providing similar products to create a competitive moat? In short: are there any barriers to entry in this business and how does Groupon keep other businesses like kgbdeals, Google, Amazon, and others providing complementary services from gaining enough market share to change the competitive dynamics of this business?