Sure Groupon clone is a successful business model. If you have an idea about starting a groupon clone website, try this free script http://www.ndot.in/products/ndotdeals-opensource-groupon-clone/
The Groupon model is dead and not profitable. It's a scam on retailers. The deal sites are supposed to bring in new customers who wouldn't have purchased something otherwise. However, the margins are very low at best on those new customers that are aquired - and sometimes existing customers take advantage of a deal when they otherwise would have been willing to pay full retail price. Also, the retailer often will take a loss on the first transaction in the hopes that the new customers will come back again. However, deal hunters, by their nature, want great deals, meaning they are going to be less likely to pay retail prices in the future. FACT: Retailers can make more money without using groupon.
I would say that if you were the starter of the idea ( like Groupon ) and you would get 6 billion $ from Google ... you would skip the 400 millions loses per yer. However if you are not ... profits can be made really hard!