Because they built up a heap of infrastructure required to consistently offer some of the best prices for goods online. Competitors could only really compete in

Because they built up a heap of infrastructure required to consistently offer some of the best prices for goods online. Competitors could only really compete in niches because the startup costs to get to amazons scale would be massive. With group deals, all someone has to do is setup a basic website and start calling up companies to find better deals than Groupon is offering, the customer doesn't care which deals site is offering a deal as you can signup to a new one in about 5 minutes. With the deals site I've found aggregators to be more useful than the individual sites as the one which has the deal doesn't matter much. If I was looking for a book I wouldn't worry about an aggregator but head straight to Amazon or Book Depository which is also now Amazon owned.