I remember visiting Yellowstone as a teenager and being upset that I was not allowed to take even one tiny little insignificant rock home as a souvenir. Up to that time, I always brought a rock home from places I enjoyed. What difference could my little memento make?
Then I looked around. Thousands of people were here with me, and if I was the only one who ever took a pretty stone, there would be no problem. But what if half of them wanted rocks, too?
Read more at Leaving a Light Footprint in a Far Away Place.