My wife had a couple of C-sections, the first one with by doctor who had 5-star Yelp ratings and the next with a one rated a bit higher than 3 stars. But the results were opposite.
The first doctor, despite having to do so by law, never showed up to check up on my wife while she was recovering in the hospital. My wife was very weak and lost a lot of blood and the scar was large and unappealing.
The second doctor was highly regarded by the staff of the hospital. After the C-section he performed, my wife was able to [slowly] walk on the third day and didn't take any pain medications after the second day. He fixed the scar left by the second doctor. My wife had a lot more energy. And he checked on her daily while we were in the hospital recovering.
When we mentioned the first doctor by name to the staff of the hospital, they were surprised we chose that person. Yet, the Yelp ratings were reversed. How could this be?
After this experience, my wife wrote a couple of reviews on Yelp. A negative review for the first MD and the positive for the second. When I checked, I discovered that the first (negative) review was "filtered out" and did not count towards the overall score of that doctor. So she still has a perfect 5-star rating, even though the ratings on doctor-specific web sites are reversed and people in the hospital uniformly know the same.
I discovered similar occurences when I wrote negative reviews on Yelp for some businesses but not others. And as far as I recall, my positive reviews were all visible. Later I found out something else.
According to several business owners and people who handle Internet marketing for companies I talked to, Yelp has a "premium" service, whereby they call you and offer for a monthly fee to manage your standings. You make your own conclusions, but I will no longer use Yelp unless I have to. And if I have to, I will definitely pay attention to "filtered out" reviews accessible by clicking a link at the bottom of other review.
So what is the point of a site where you don't get a truthful picture? Fortunately Yelp has competitors.