In reply to Euge:
Got to agree with all your sentiments, not so long back saw a guy drop a load of litter whilst walking. I picked up what he'd dropped and caught up with him and told him he'd obviously lost the carrier bag full of his rubbish i'd picked up.
I got the expected load of abuse, being called a w****r etc. I just laughed at him told him there was only one of the above about and brought it off the mountain myself.
To be honest me and the wife tend to take a few carriers with us on walks now and fill them with any rubbish found and bin it when we get back. We can't take everything we find but we like to do our bit. Even my kids who are 6 and 10 comment on the rubbish and will bring empty bottles etc down in their packs (obviously not the ones that are full of urine!!!!).
I know its frustrating but you can only do what you can do, we have to try and educate people. I know charity groups tend to get a lot of flak for this but I've seen folks who appear to be seasoned walkers drop litter too, you are always going to get the odd "bad apple" after all.