Yelp Reviews Are They Real?

Have you ever read Yelp reviews that rave over a restaurant and find very few non-raves then go to the place and find it to be less than 4 stars. Well a restaurant in San Francisco is accusing Yelp of something that people have wondered about for years. They say that the sales people at Yelp told them that if they bought adds on Yelp they would find the bad reviews disappearing and good reviews appearing. Salakjit Hagerty owner of Bai Thong Thai in San Francisco claims that customers have told her they have written good reviews of the eatery on Yelp but they have never appeared.
Yelp naturally denies this. They say they have algorithms that remove what are considered bogus reviews. They keep these algorithms secret to dissuade hackers. The company denies any pressuring of businesses to advertise on the website for better reviews.
I personally have seen adds offering writing jobs as yelp reviewers. The job offers state you don't have to actually go to the businesses looking for good reviews. These jobs are of course on Craig's List not known for its honest posters so who knows if they are "on the level".
Business owners I know have been pressured by Yelp's advertising sales staff to by adds but none have ever mentioned being offered good reviews by the sales people. They did tell of constant phone calls though.
In this day of the Internet one can never be sure of what one reads. Perhaps the restaurant is wrong but maybe not???