This answer states Chafetz Chaim's 7 rules regarding to'elet for Lashon Hara.
When a service provider posts his business on a ratings site such as a doctor's site like Zocdoc, or one of the travel sites like Expedia, or a store / restaurant site like Google or Yelp, that owner expects to receive reviews - both positive and negative. He hopes that overall, the number of positives will far outweigh the negatives, but, of course, there is no knowing this. He also is able to defend himself by posting his own comment to respond to any problems. Additionally, sometimes, even the negative comments may be useful to the service provider so that he can know about problems and improve the service.
Can we, therefore, assume that when one posts his business on one of these online sites, and knows that people will comment, as that feature is built into one of these sites, does this mean that he knows in advance that some of these comments might be harmful to him, but is taking that risk? And, if he's taking that risk, does that mean that any negative comments that might harm him may be permitted and therefore not considered lashon hara since, in a sense, he allowed such comments? Would that stipulation, therefore, allow someone to post negative comments without worrying that it is lashon hara, or that all comments would be considered to'elet?
Note: For this question, I assume that the provider / owner is Jewish.