This pretty much coincides with my experience; when I'm with a group of friends and we are using a Groupon, we get about 1 star less worth of service. (I've never used one on my own; I'd rather pick the restaurant on my own rather than being told where to go buy whoever happened to feel like buying an ad that day.)

That's why I don't get the Groupon hype. It seems like a way for businesses to pay money to upset customers. Probably a bad idea.