Our trails at the forest, at least within 5 miles of the trail head, are pretty busy. horses get used to being passed, oncoming riders you need to get out of the way of, and that kind of thing. Strangers coming and going wouldn't throw Bay's cool, but anyone we've been with who suddenly takes off makes him get on the muscle, yeah.
Belle was funny, some rides she wouldn't pay the least amount of attention to the other horses, then the next she'd be jigging everytime one went past.
I never had trouble if she and I left someone, it was only when they left her.
Becky