Wait that's how you validate oscm's? I could totally fake one and make it look so real.
I think they might also ether actually talk to a lot of them or e-mail a good portion of them through their websites or other known places.
To fake it well, while not impossible, one would also need a large number of candid pictures to work with or at least one where the person is holding up a sign or where they are positioned just right, if that was the only method, and it might not be. They could have another picture where they ask the person to do something other than just have a sign, like holding up a certain number of fingers for example. Or at least that's what I would do.