I left a poor review for an employer only one time in the 10 years or so I've been on Glassdoor (there were only a couple other reviews). And almost immediately

I left a poor review for an employer only one time in the 10 years or so I've been on Glassdoor (there were only a couple other reviews). And almost immediately after, there were about 20 or 30 5 star reviews posted in a short amount of time. The company only had about that many employees, which proves that the CEO (or someone at the top) either told everyone to write a good review, or some of them were fake, both clearly 'incentivized' by any sane definition of the term. I reported this to Glassdoor and they refused to do anything about it, and I even had the report escalated and re-reviewed, without any effect.