Crowdfunding is a promising idea, and has created useful products. The Canary home-security system I wrote about recently was funded in this way. One big problem remains, though: how do you reward your early backers if you become too successful? Many of the 9,522 people who provided $2.5 million to fund development of the Oculus Rift headset on Kickstarter were understandably miffed when the company was sold to Facebook for more than $2 billion, of which they received precisely nothing.