The reDesign blog ran a critique of the standard Groupon merchant contract recently. It's worth a look.
Just because there are merchants that are dissatisfied with the Groupon experience doesn't mean that it's a bad deal. In fact, the longer you are on Groupon as a user the more you see the same offers come back for more. In other words, clearly it's a promotional gamble that some feel bears repeating. Still, just passing along the link to a critique.