Craig Mount posted a detailed analysis of a Yelp update being named the Ghost update over at Search Engine Land. In short, sometime around October, Halloween time, Yelp dropped tons of reviews in their results and in some cases, it ended up listing them as "not recommended."
He said one of his clients "lost 40 percent of his total reviews to the “not recommended” section of Yelp" by November time. Craig checked other business and quickly found he was not alone, "some businesses had lost over 1,000 reviews" he said. Yelp wouldn't really comment but he said "Yelp’s recommendation software and it was now recommending fewer reviews for public consumption."
Craig's post at Search Engine Land goes deep into what changed - I highly recommend you read it if you are at all into local SEO.
There is a lot of discussion around this Yelp Ghost update in the Local Search Forums:
Yelp updated its "recommendation software" around November 8th. The result was a massive wipe of thousands of reviews.
Thanks for bringing this up. I have a client I just checked who is in auto repair. At the beginning of November they had 42 reviews on Yelp. On December 7th they had 38. Today they have 35.
FWIW, I asked Yelp via Twitter if they had an algorithm change and they responded with, "Which reviews are recommended on business pages will change over time as the software picks up new information that makes a reviewer more trustworthy, or the information we have about a review grows stale."
Forum discussion at Local Search Forums.
