Since Chaff is excluded from the main recent thread view, I missed this precious thread. I'm 4 months late to the topic, but since I'm at work, sure why not.
When I see someone let their dog go #2 on my front yard without picking it up, I call them on it "Hey are you going to leave that?" the typical reply is that they don't have a dog poo bag. Of course I happen to provide one immediately.
If they don't comply, then I threaten to take a photo and call the hot fuzz Sylvester Stalone "I am the Law" judge Dred.
but on the trail it's different somehow. I expect the person to bury, cover and hide the captain's log.
Speaking out, versus expected outcome.
Can't just insult the person, you need to convince them to change behavior.
Assess the odds of changing someone's behavior.
Their age and their gear type implies someone with a specific mindset.
Is that person mentally insane, armed, high on drugs? will you continue running into them for the next few days make the trail a terror?
You can also approach with comedy, usually works better than confrontation.
Compliment instead of insult:
"That's a prize winner! must be at least 8.5 Curic"
South Park reference: http://en.wikipedia.org/wiki/More_Crap
"Whoa Buddy! help us keep the Lock ness monster out of the lake"
"Gotta hurry and bury the Frankenstein monster before it comes back to life!"
You might get compliance that way, or start carrying a gun and get medieval on his a..