1) Businesses that exist solely because of daily deal sites
2) Businesses that have successfully leveraged daily deal sites but won't share their stories
#1 is a lot more common than you realize. I know a photographer who makes 6 figures teaching workshops that would have been impossible to market without daily deals. He essentially created a business based on his deals. There's an old woman in SF's Chinatown who gives "ghost tours" of the neighborhood by selling $25 Groupons. Before the daily deal sites came along, she was a waitress...now she pulls $70-$80k a year setting her own schedule and doing something she loves. Again, impossible to market such a thing without Groupons. I recently attended a class on coffee/tea appreciation. Hugely successful for the owner, and lots of fun for attendees. He told me this was only possible because of daily deals...he had no notion of "regular customers" or "full price" customers before the deal sites came along. His business simply didn't exist.
#2 Businesses who successfully leverage the deals model aren't going to go blog about it or tell you exactly how to replicate their success. They're afraid that if competitors find out their little secret, they'll lose their advantage, formula, etc. The truth is there are lots more businesses who've been successful with this model than there are "victims". You just don't read about them because successfully leveraging daily deals is almost a trade secret of our time.