I was an avid hiker long before I ever got on a mountain bike. I have ridden horses and have enjoyed it greatly except in those cases where the horse knew he had my number and took advantage of that fact. Among my good and best friends are horseback riders and hikers. I am simply trying to make the point here that mountain bikes and their riders are not the enemy of the trail or other user groups. I do understand the legitimate concerns of horseback riders in those situations where a bike rider might ride up on the back of their horse unannounced and try to pass.
Education is needed here.
Education for the rider not the horse, of course. Many mountain bikers have never been around horses much if at all and consequently do not I am sure understand that a horse is most likely to be spooked and startled by what it does not know or recognize. Horses simply are rarely ever exposed to bicycles and certainly do not spend a lot of time around them. Bikers, yield to horseback riders and announce yourself to both horseback riders and hikers and then we can all get along. I firmly believe that most bike riders do this anyway.