It is interesting to note some counter examples though. A real estate agent books only the commission as revenue, not the price of the property. A stock broker does the same. A delivery company that delivers something COD, also only books the fees, not the value of the goods. The question is, is Groupon acting more like a broker/agent, or are they responsible for making sure the service is rendered? It is not obvious, so there is some logic to the SEC saying Groupon should record revenue as if they are an agent/broker.

Either way, the initial comment that "OMG, Groupon are obviously crooks", is misinformed.