If I wore a mask like the Lone Ranger, how hard would it be for people to recognize me? Does it have any benefit at all? 
Can’t know until you try…
Tom Rainbow (author of several memorable science columns in Asimov’s before his early death*) wrote back in 1983 that with facial recognition software, no mask was safe (even a full cowl). Byt now, it would be even harder to keep things secret.
*As a hero: he saved a child from being hit by a subway train.
I find the full faced cowl recognition solution very hard to believe, unless you have a high enough resolution camera to map the iris. In that particular case, well, the iris is pretty much unique. The classic example is the case where they located the woman on the National Geographic cover with the incredible eyes. I’m under the impression that face recognition algorithms depend on well defined metrics that that are very similar to those that human brains use. There are certain dimensional metrics such as distance between eyes, nose and mouth, width and height of those features, and key features of the shape of one’s head.
On the other hand, I can’t recognize a single god damn person if they are wearing sunglasses.
How are you with married god damn people?
Every woman I hit on tells me that they are married. It’s uncanny.
In my world, they’re all married to each other! 
But who shaves the barber?
I don’t get how any non-CSI computer could get a match with a full-faced mask (assuming that’s what is meant by cowl. If it’s looking at the iris, well, then it’s an iris-detector, not facial recognition. Is the claim that it can recognize the pupils to such a degree that there is a unique-to-the-individual measurement that can be done? That is, could facial recognition be down to just this one measurement? Or are there other semantical shenanigans going on, in that it reads heat or whatnot behind the mask?
I find that a winter cap sometimes causes me difficulty in initially recognizing a coworker or casual friend. Something about the hair being covered makes the person look sufficiently different that I might pass by without saying hello, unless I happened to look closely. So the Lone Ranger’s mask and hat together might obscure his identity a fair amount, at least for casual viewing.
Of course if I were Green Lantern, I would use my ring not just to hold the domino on my face but also to obscure my features and alter my voice a bit.
Certainly worked for The Spirit.
No kidding, those are called domino masks? I was picturing a person with dominoes stuck all over their face and was wondering why you would want to identify that person at all.
I dunno. Suspect in black-on-white crime?
Interestingly, you may not be that far away from the actual etymology - you just have it reversed. From the AHD definition of the game tiles:
For the second definition concerning the mask, they say:
So people parodying the church Latin of the Catholic liturgy as “Dominoes, Dominoes …” are also closer than they know.
In some of the earliest Lone Ranger movies, the Ranger wore a two-part mask. The leather domino mask covered the area around his eyes, and a black gauze veil covered the nose, mouth and chin. It looks a bit odd, if you grew up watching the Clayton Moore version, but it did a better job of disguising him.
Now that I think of it, the domino mask would be a dismal failure as a disguise in the Old West. You’d just have to look for the guy with the raccoon-like tan line and that would be your incognito wannabe.
Yeah, but if youre far enough West it might actually be Zorro, instead.
Would a Stetson shield one’s face enough that there wouldn’t be any such tanning around the eyes?
I remember in Micheners’ Centennial, one of the cowboys explaining that real cowboys are tan on the lower half of the face only for exactly that reason.
All things considered, I think the Lone Ranger’s mask does a lot better job than Clark Kent’s glasses.
Yeah, but with Superman you have to take into account that, not only does he take off his glasses, he also redoes his hair, and stands up straight. It’s still silly, but the difference in demeanor is the real difference. Well, that and the fact that for most people he’s just a blur in the sky. Lois Lane still has no excuse for not being able to tell.