There are several prominent local pooners who won't post negative reviews on PERB because they're afraid of someone jumping on them, not necessarily the ladies who are the subject of the reviews, but their admirers and, in some cases, shills. I know this because these pooners told me so in PM's. I don't understand that attitude at all, but it definitely exists. I also think that one of the problems is that some people lack sufficient reading skills to distinguish between an honest report on a so-so experience and a personal attack on the subject of a review. I've been fortunate to have had very few negative experiences since joining this board, but I've never been afraid to report them. If someone takes exception, frankly, I don't give a shit.
While there's an obvious social aspect to this board, its primary purpose is to enable the exchange of useful information re escorts and their services. If only the positive experiences are reported publicly (excluding the fake reviews by the "pathetic shithead shills" so eloquently described by dirtydan

), we can't even determine the extent to which a lady is YMMV, let alone decide if we want to see her.
Granted, negative reviews are more difficult to write well than positive reviews, because the reviewer has to be careful to avoid the temptation of name calling and abusive language, and instead concentrate on reporting what was wrong with the encounter and why. However, it can be done, and the review needn't be long if it contains the vital information.
Just last week, a very prominent local SP told me some of her clients have had negative experiences with local SP's but, in her words, are "afraid to post them because they fear other SP's will refuse to see them". How pathetic is that?

And, I doubt very much that that would be the case anyway, unless the reviewer had posted personal attacks, rather than reliable reviews.
I depend on other reviewers posting honestly about their experiences, whether positive or negative. I know some newbies feel put upon when they're accused of being shills, but if they post a couple of obviously legitimate reviews, the doors will open up for them very quickly. I only share info via PM with other posters that I trust. That trust comes about by reading their posts over time. For me, a well-written negative review is one of the most reliable indicators of whether or not I can trust a poster.