I worked for a while at a company that everyone hated, and there was an ongoing war on Glassdoor between the narcissistic CEO and the employees. Every new employee (and there were a lot of those because turnover was high) left negative reviews, and periodically the CEO would get on with a bunch of sockpuppet accounts and leave positive reviews. It was a small enough company that we knew they couldn't be real (they claimed roles that were all accounted for, and they'd all show up over a day or two with the same writing style), but Glassdoor has basically no verification and never responded to our reports. The only action their moderators ever took was to remove our reviews if we tried to call out the inauthentic ones.