An army of clone websites that copy the daily deal model and dilute the brands that are legitimate, Weintraub says.

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The Groupon model is easy to copy, so dozens of local clones will eat Mr Mason's discounted lunch.

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In fairness, everyone seems to be trying to copy the Germans in using alphanumeric model designations, and most of them are awful.

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The revenue model behind Groupon is simple to understand but, according to critics of the company, easy to copy.

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