Rachel Swaby wrote a great piece for Wired on the complex problems that Dropbox had to solve to arrive at the simple solution they have today. This sentence stopped me in my tracks:

Almost immediately, those who didn’t actively search out the solution outnumbered early adopters.

Think about that. About 100,000 early adopters signed up for the Dropbox service in the six months leading up to the official launch. But because these early adopters started sharing folders with coworkers, friends, and family, they immediately hooked an entire network of regular users into the service.

Dropbox solved a problem most people don’t know they have, and made the solution simple enough so that non-tech savvy users immediately get the beauty of it and how it can fit into their lives. That’s innovation.