At 17, Sahil Lavingia helped design Pinterest. Then, a year in, Lavingia left. Now he’s starting Gumroad, a new service which he says will revolutionize social shopping and e-commerce—and maybe even alter the way people create. Here’s how it works: Say you’ve made something—a song, a blog post, an app, etc.—and you want to make a little money from it. Just upload it, price it, then Gumroad, whose slogan is, “Sell anything you can share,” provides you with a custom product URL that is easily shareable across your existing social networks. Gumroad makes money by taking a 5% cut out of each purchase.