I have no problem with a lady wanting added discretion and security by hiding her face. In these days of photo-shopping and airbrushing and who knows what else, you don't really know for sure until you're standing there anyway.  Much more important to me is that, whatever you do show, it should be accurate. In the last month I've seen ladies who were substantially different from their photos, either because the photo was of someone else or years old.  Do what makes you comfortable, but be accurate.  

As for success, of the few hundred ladies I've seen over the decades, I would wager that at least 65% didn't show their faces (back in the pre-historic era you were dialing fromtheYellow Pages; Google if you don't  know what that is). And I was no happier or unhappier with them than the ones who did.

I have a tougher time selecting a provider who hides her face, especially in the absence of multiple, detailed reviews.  
.
I absolutely support a provider's right to show as much or as little as she (or he) wants. But I want to fall in love with my provider's face, body and personality - at least for the hour or two we are together.  
.
Unfortunately I've been disappointed too many times by hidden face, fake, altered, or old pics. And I'm not fond of throwing away hundreds of dollars or more on an experience that started off poorly due to (what I may perceive as) dishonesty. Though I fully understand that the provider's intent was (probably) safety, if I feel like I'm not getting what I expected, I'm not going to enjoy the session.  
.
Life is good.
.
The Cat

I completely agree with herbtcat.  Couldn't have said it any better.