I generally assume their ratings are gamed, especially for smaller shops. I know I've been asked recently (in the last year) to review the company I'm currently working at on glassdoor by a superior. As you can imagine, I gave the place a good review.
A year later, they've laid me and all but 1 dev (the CEOs buddy) off and failed to do basic shit like send COBRA info and agreed upon severance payments, but their glassdoor doesn't reflect that, because glassdoor doesn't make it possible to edit reviews past 30 days. I suppose I could go delete the review at least