Well, it's not a big deal here; mostly it's the non-horse people that want to take photos, usually they want a photo of themselves and one of the little horses. If the photo comes out really bad of the horse, they don't care. It's unlikely that anyone outside their immediate families will ever see those photos, so no harm done.
However, I know very well how a bad photo can ruin a good horse, and honestly there are some people that I would prefer that they not bring their cameras if they come here. I know farms that do not allow visitors to take photos, and I can understand their point of view. They spend big money to promote their horses, and a visitor that comes and takes a bad photo and then passes it around to other breeders or buyers can do harm to their promotional efforts. And yes, for sure a bad photo can make a good horse look bad. Very bad.
I've been given some photos of a World Champion stallion at home in his paddock--taken by a friend when the owner wasn't around, and I'm quite sure that the owner would not be happy to know that those photos were taken. If I were to post those photos here for you, you would never guess who the horse is!!