The shortsightedness of trying to anonymously damage your former or current employer's reputation (thereby damaging your own reputation) never ceases to amaze. It's akin to graduating with a degree from university and then anonymously trashing that university causing damage not only to the university but to the value of your own degree. Why would you do that?
Let's say you are successful in convincing the world that your former or current employer is a horrible company and that management is incompetent. You now have on your resume the fact that you worked for a horrible company and learned from and were mentored by incompetent people. Doesn't exactly help your chances of landing that next job or the job after that, does it?
I know this will likely fall on deaf ears, but I felt I had to say it as the people writing these angry posts, if successful in their mission, will not only be hurting the company and management, but also recklessly hurting their current or former colleagues who ever worked at the company, and also hurting themselves. Perhaps you are good people, and if so, I hope you give some thought to the innocent people you are damaging (and if that's not enough, to the harm you are causing yourself).
If you mistakenly believe that posting angry posts on some revenge board is an effective way to get management or the company to change or do things differently, you should rethink that approach. Private discussions with management is far more likely to induce changes.
Anyway, thanks for hearing me out. God bless.