I would never just walk past someone, I always say hello, sometimes stop to talk about the weather, trail conditions, etc.. One of my biggest pet peeves is to look someone in the eye, say good morning, and they just blow me off and keep walking, makes me sad.

However, speaking of pet peeves, my biggest complaint are trail runners coming at me from the uphill side when I'm lugging my pack, storming the path and nearly knocking down anyone who doesn't jump off the trail to make way.  One....of.....these....days....