>40. Penny Problem Gap: Economists assume demand is linear, but people’s behavior totally changes once an action costs money. If the inventors of the Internet had known about it, spam wouldn’t be such a problem. If sending an email cost you $0.001, there’d be way less spam.

Or, more likely, the internet as we know it would not exist and it'd just be some crappy failed commercial venture where everything cost money and it never took off. Building commerce into protocols is a terrible idea.