Dropbox doubled its users last year, from 100 million to 200 million. How? By constantly expanding itself into people's digital lives (while fending off the likes of Apple, Google, Microsoft, and others). "We want you to be able to say, 'I know where all my information is—it's in Dropbox. Everywhere I go, whatever device, whatever application, I know that I can pull things out of it,'" says product manager Sean Lynch.