I found this story interesting on how this guy built an egg shaped tree house. He did it illegally in secret in Canada's Whistler forest just yards from multi-million homes
he said it took months to find the right tree to build on, and when he did the spot was on public land looked down on a row of multi-million dollar homes.
The computer technician-turned-carpenter started off by creating a scale model of his design to test its strength and durability, before beginning the months-long quest to find the perfect tree.
I don't think I would want to live in this during a storm or the Canadian winter, but would be great to experience it for a while and a great way to experience living in natural settings for a while.