ACKNOWLEDGEMENTS
This paper has benefited from many conversations with Lyra Colfer, Joachim
Henkel, Rahul Kapoor, Venkat Kuppuswamy, Karim Lakhani, Jianxi Luo, Christina
Raasch, Eric von Hippel and Jason Woodard. Detailed comments by Alden Hayashi
improved the paper substantially. Any errors or omissions are mine alone