I had written a negative review of my former company. It followed guidelines and was completely factual. When the company complained... the review was deleted. I re-worked it and put up a watered down version of the first review. It was accepted and then like the first... a few days later, it was deleted. I just wrote and submitted the third review...
On the site they say that they don't remove negative reviews at employer request but this is a lie. They delete them once the employer/company complains.
UPDATE: 4/17/2016. They deleted my review again after a few days. In addition, there were six or eight other reviews that were negative, some scathing but all within guidelines. All of those were deleted as well... Glassdoor.com deletes reviews if their sponsors complain. Don't expect the straight story from their reviews.