Lots of mountain walking around here - and not quite on the scale you have over there, so the population is a bit more condensed. It's not a problem if I'm "wild" walking, but if I follow the trails at the busy times, there will always be someone who has been "caught short" - often kids, I imagine.
Human poo is unmistakable - the stench!! Mind you, some dog poo isn't pleasant either, especially if the dog eats a certain brand of food (sadly I can tell!).
Maybe I have never run across it...the only questionable instance I can think of was a large pile with a load of undigested corn in it.
