Over the last eight years, Ben Silbermann has quietly built Pinterest into a global brand with 250 million active users. He's the cofounder and CEO of Pinterest, the image search tool that lets users save and share their favorite photos, designs, and recipes. Pinterest could hit $1 billion in ad revenue this year, and it is valued at $13-15 billion. But Silbermann doesn’t want to be just like all the other big tech brands. He wants his site to feel like a real community, even as it grows larger than he ever expected.