I agree, I think that the onus is with the posters on how they approach it. Posters who launch a tirade (usually poorly written drivel) against a school and then refuse to hear any other opinions about it (as so often is the case), shouldn't expect to be taken seriously by readers or the school in question!
A well contructed argument that allows one to make one's own judgement and allows (even encourages) a right of reply is far more valuable for readers. I hope (by having admin present the criticisms) that TEFLwatch can achieve this line of discussion in the public rooms. Any schools then visiting the site, will hopefully see the nature of the forum and be less likely to dismiss poor reports.