The Aardvarchaeology blog looks at the ruins of children's treehouses, which can often be found in wooded areas near residential areas. There's a big difference between the way that kids and adults abandon their sites — children leave everything in situ, forgotten and frozen, while adults strip a site of everything that might be useful.
And the treehouse sites are hardly ever cleaned up. In fact, the children's parents often have only a vague notion of where the treehouse is. They may help to build it, but they don't feel responsible for it. It's out in the woods where only children and mushroom pickers see it: out of sight and out of mind. The mess there would never be tolerated in the back yard, just as most Westerners of today feel really uncomfortable in the stench and litter of Third World villages.
So the next time you come upon an abandoned treehouse site, you might give some thought to the fact that you're standing in the ruins of someone's childhood. The children who used the site no longer exist: they're grownups now, living somewhere else, disposing more rationally of their belongings. And some of them very probably have kids of their own now who are wheedling them to buy a few boards and a box of long nails, a rope ladder and some tarred roofing cardboard. And daddy — can I please have your old drum kit / dough mixer / rollerskates? I'll take them out of your sight.