Dropbox

Dropbox has some of the smartest — and nicest! — people around.

The company is growing rapidly, which means there are more interesting problems to solve and growth opportunities than there are people to solve them all. It's also a chance to see how things really work at a high-growth company; management is extremely transparent.

The problem space is well beyond simply file sharing at this point, and there are plenty of interesting new projects in development for product-focused folks. Our infrastructure challenges are second only to a handful of companies (like Google or Facebook), but we're getting to build that infrastructure from the ground up, with a chance to learn from those that have come before us.

For some folks, the constant change might be a con. Dropbox is growing incredibly fast, so everything that worked a year or two ago needs to be re-evaluated against higher scale.