A while ago I made a date and time certain apppointment with a visiting top-rated provider, whom I had seen several times on previous visits.  Soon after, I got a msg saying I needed "re-verification," no further explanation.  I can only guess that her current helpers ask for at least three current references, and I have furnished neither reviews nor references for quite a while, always relying on the fact that enough people in my area knew me.  
When no further response was received, I canceled my appointment reluctantly, with a note explaining that I respected their need for whatever measures they wanted for their comfort, security, etc.  After all, it's their game and they make the rules and there are enough horror stories so that precautions are necessary.  
Although I was disappointed at the lost appointment, I made a quick call to a regular and early the next day I was on her doorstep, no muss, no fuss.  Perhaps the prospect of deprivation inspired me, but I had a great time with a wonderful person.  
What to make of this little story?  For whatever it's worth, the unique aspects of this part of the entertainment world ensure that the hobby will always be in flux and evolving.  Some current operators, like the above, run things like a private members club, restricted entry, very few new members.  They can do this because they offer genuine quality, and top providers know they can see anyone they want.  But in time, this practice too will change, I predict.  Operators have to stay one jump ahead of those who would disrupt their business, and for that reason we have to stay nimble and flexible too -- always conduct due diligence, and maintain situational awareness.  Anyway, despite my stress on due diligence, I have to admit that the person I ended up with in this story I met through sheer dumb luck, no due diligence, no reviews, no word of mouth.  But a world in which such things can happen, albeit not often, is still pretty wonderful, in my view.