Chris Dixon argues that breakthrough technologies like the PC, the web, and open source often start as hobbyist projects, because engineers pursue what interests them while business people chase near-term returns. He bets that today's hobby projects, from Bitcoin to 3D printing, will become the industries of the next decade.

• Engineers vote with their time and business people vote with their dollars, so hobby projects are where the smartest people explore ideas not yet constrained by short-term financial goals.
• The PC, the web, blogs, and most open source software all began as hobbyist work in garages and dorm rooms before becoming large industries.
• He names current hobby projects with momentum, including math-based currencies like Bitcoin, NoSQL databases, the internet of things, 3D printing, touch-free interfaces, and Kickstarter-style hardware, as likely seeds of future industries.