Normally I would agree that education is the answer, and I expect for most people that it all that is needed.  Unfortunately, there is a segment out there (and it appears to be rather large) where it just doesn't take.  As an example, before through hiking the AT, you have to obtain  a permit and agree to LNT and a few other things.  A few years ago, I had the opportunity to backpack in the Great Smokies and part of our trail was on the AT where we had reservation two night in the trail huts.  One hut had a composting outhouse which was really nice, but the other just had a sign that pointed to a meadow.  We went out to the meadow and it was covered in toilet paper and excrement.  It was the most disgusting thing I've ever seen.  We went and found our own place and barried and packed out.  Most of the backpackers we saw on the AT had shovels hanging from their packs and all but a very few were still nice and shiny clean.  The Great Smokies is 3-4 weeks up the trail from the start in Georgia.  Those plastic shovels, no matter how well you clean them after use, should be scratched and dirty by then.  Unfortunately, there are people out there who just don't care and or don't think, at least not about others or the environment.  Even after "agreeing" to shoveling and packing out they still do as they please.  The big question is:  How do we get through to these people?