Is it Permitted to Leave Negative Online Reviews?

Question: Is it permitted to leave negative online reviews for online business, such as Amazon sellers who are Jewish? Is one allowed to read a negative review about someone else? 

Answer: If the seller is doing something wrong, such as hiding defects in his merchandise, it is permitted to leave negative reviews to save people from being harmed by him, as long as the seven conditions of the Chofetz Chaim are met. 

If he isn’t doing anything wrong, it would seemingly be forbidden to leave a negative online review. However, many Poskim say that platforms like Amazon are an exception to this rule. They note that the entire platform of Amazon is based on the feedback and rating system. When one signs up to do business on Amazon, he is agreeing to this system; therefore, it is as if he was mochel anyone for speaking Lashon Hara about him in this forum, and it is understood that anyone can post their honest opinions and read the reviews.

Obviously, the criticism has to be constructive and not exaggerated. 

Question:

What about Google reviews, where the business did not sign up for anything?

Answer:

In that case, the above leniency would probably not apply.