A paper by Georgios Zervas, John Byers, and Michael Mitzenmacher explores the relationship between a Groupon surge (like when a small bakery has to make 100,000 cupcakes) and a drop in Yelp ratings. Tim Worstall at Forbes explains:
Imagine that you are an enthusiastic and regular consumer of the finest chimichangas that you can find. You’ll likely have scoped out your neighbourhood, tested the chimichangas on offer and zeroed in on those places that make excellent ones. You might even provide reviews on Yelp pointing other enthusiasts for the comestible so as to guide them to the good places.