Yeah - I have to say, climbers (and I is one, too) are amongst the worst culprits. Oh, and runners (no pun intended). Hikers don't tend to be as bad as it's easy to carry a plastic trowel around - not heavy. I did some climbing in Europe a while back and the campsite was like it was festooned in Tibetan prayer falgs - on closer inspection, they were not Tibetan prayer flags.
There are some very good guidelines around somewhere on how far away from water to bury waste, how deep, etc. I expect someone should be able to find these as they would be useful.