The funny part of this is that if you look at his list of reviewed places he has a bunch from Chicago, IL, then the 2 for the 2 locations of Sauce in SF, then another place in Chicago on the SAME DAY.
Now I know that you could wait to review places, but that certainly seems like a suspicious line. Also 2 of the 3 total reviews he's ever given a 1 star rating to are Sauce (out of 71 total reviews).
I thought the same at first and honestly expected that the guy had just flat out committed libel. But after a tiny bit of research, I found that his claims about the restaurant's cleanliness were in fact accurate. (http://bit.ly/16xkdCO)
So while he probably was just writing the review to help his friend, his review is informative and factually based so really, there is no reason to remove it or the guy's account as far as I can tell.
This also makes Andy J's threat to make his active Yelp friends aware of his discontent with the restaurant make all the more sense as they are obviously better at it than him.
Actually, I could see small businesses paying for a service that tracks Yelp and other review sites for "interesting" activity based on patterns like this one. Perhaps getting information from other sites to figure out who the reviewer works for.
You should patent this: "a system and method to filter Yelp reviews based on Groupons offered in locale" :)