Pre- Fab Designer Tree houses

http://www.danielswoodland.com/theming/themed_environments/index.php
Advantages:
Novelty
Attractive to children
Quickly to build
Variations on a Theme :different types of theme

Disadvantages:
High price
It need a spacial location
Because it made by wood, it is easy to break
Not easy to protect , for example bad weather can effect it .
Not easy to find material, it must need high quality wood.
Heavy
fire