"One mom said she had built a tree house with her sister, but she would not support her children's interest in building such a structure, because she's afraid they'd fall or pound a nail in a finger."
Yes. They'll fall. Break an arm, have the wind knocked out of them, all sorts of scary bad things.
Yes, they'll pound nails into fingers, hands, feet, legs, and arms.
And when Mommy bans them from a treehouse project next door at Billy's house, they'll start another one around the block in Johnny's back woods.
Seems like my youth was one continuous treehouse project from age 10 to 16.
Then we bought 5th hand autos, and that was the end of that. We bequeathed the treehouses to our younger gang of siblings, so that they could have some fun.
aw heck, i want one!
http://www.thetreehouseguide.com/press/latimesaug052004.htm
heres some gorgeous places!
http://www.treehouse-company.com/price3.cfm