Whenever I go to an ESL forum I always make sure I bring in a healthy amount of skepticism and a thick skin. Most people on this forum, I believe, are intelligent enough to know that when people bad mouth a school it might not be the schools' fault. It might just be the foreign teacher venting their frustations. Human nature is such that people will defend their actions even if to an outside observer they are simply wrong. This said, schools might just bad mouth a teacher for no good reason. In this case due diligance is do by the person who reads such posts, and especially those potential teachers who might go to that school and are now aware that they neeed to investigate their potential employer even more. If such school has multiple complaints, then one is better off staying clear of such a place. Can so many people be wrong?
In China, I don't know about Vietnam, Chinese employers are known to over promise and under deliver. Outside this forum I have read of teachers being deported to avoid being paid, teachers brought to teach illegaly, hazardous living conditions, teachers being beat up (this from a friend who told me) and even a few mysterious deaths.

This forum serves as the canary in the coal mine, per say. You might not like some of the posters here, I don't. You might not like what they have to say many times, I don't. But darn it, it is their right to say it and I am glad they are honest enough to say it and this forum is open enough not to censor those comments.

At other websites it is not allowed to write a negative review about certain advertisers, thus unscrupulous employers can continue to advertise. These places, if they are not sound working places, should be exposed for what they are- sham places.