I agree.
What a lot of people don't realize is that Amazon has amazing logistics and considerable skill in merchandising. Building that logistics footprint is why Amazon has survived and others failed (speaking as someone who worked for an early competitor).
Look at Best Buy and ask yourself, is Amazon really so easy to replicate?
Granted... I still don't think Amazon is worth the crazy multiple that they trade at, but you can't put them in the same class of company as GroupOn.
What GroupOn has is a brand name and a legion of sales people and contacts with local businesses. Unfortunately, GroupOn has a way of doing terrible things to local businesses that can't operate at the scale of something like GroupOn and which lack (in a sadly large number of cases) the simple business math skills to know when a GroupOn deal is no good for them.
So, the two assets GroupOn has (brand and sales/contacts) are both fairly impaired and much more easily replicated than what Amazon has to offer: logistics, infrastructure and algorithmic secret sauce... not to mention brand and customer loyalty.