In reply to French Erick: I take your point about plastic bags not being environmentally friendly but just a few things to consider.
You're carbon footprint doesn't mean a great deal when someone's kid comes over to them with your sh*t all over their hands. You're right, it's not just purely environmental reasons, but that doesn't mean we don't have to think about other hill users and their health and right to enjoy a clean environment. Maybe someone can come along and give us some facts on bugs and such like but it's a no brainer that it's best to avoid contact with rotting feaces and lets face it, if it's left around, someones gonna stick their hand in it at some point. Also if you sh*t in the snow then think what happens to that snow when summer comes and someone doesn't think before having a splash or a drink while walking up the path. The incidents mentioned in the conditions report are far too close to a water source and lets face it, people drink from streams in Scotland.
Bin liners are plastic like you say so not environmentally friendly but you can always choose biodegradable ones if it's really a concern (and not just an excuse!).
I have to say I don't see a couple of extra bin liners going in the bin being very significant in the grand scheme of things. When you think of the energy used treating water to use in our normal toilets or compared to the petrol we all use travelling to the hills then a couple of bags, for occasional emergency use, doesn't seem much. These things are much more environmentally damaging so if you're happy to do those then why not so with the bags.
and finally if anyone insists on going "behind a boulder" at the very least do it properly, away from water sources, dig down and burry it and burn your paper. (Another reason why everyone needs an adze!)
Ben