I have not seen it that often to be honest , I know it happens but really don't see it that much. I remember at one point on another site there was good reviews going out for a lady that was robbing clients and it was easy to tell that the review was bogus just based on the amount of reviews the reviewer had done.

 I myself do take the time to check out the reviewers other reviews to get a basis of there expectations and such. I am not saying 100% but I doubt any of the folks that are very active around here and very much into the hobby would bash someone because of another providers request

 
 I cant speak for everyone but I think most folks either client or provider do there best to avoid any drama while enjoying this hobby and I would suggest you try your best to just let it go even if provoked. I think back to one provider I saw who showed me a very nice time, was very sweet while together. I decided never to see her again after seeing her openly bash and trash talk other providers on another board. I had never even seen or wanted to see the providers she was bashing but just rather take my business else where.

Ten or fifteen years ago, there was a real problem with that in DC/VA/MD metro area -- more on a canine-related board and one with a street-like name than on this one.  It centered around a handful of competitive drama queens who viewed the hobby more as a contest than -- well, a hobby simply to be enjoyed and appreciated.  It's clearly better now that those particular ladies "aged out" and/or moved on.  But at the time it was awkward from the clients' perspective as various ladies and their circling satellites tried to create problems for others.  It was more about egos than business.