In early 2009, just months after Drew Houston and Arash Ferdowsi launched Dropbox, a service that promised to sync users’ photos, music, and documents across computers, Apple’s MobileMe team suggested the pair come by for a chat. The two MIT-schooled twenty-somethings knew they were in for some discussion about how their little startup was competing with the computing giant, but they were not prepared for what was first off the block:

How did you get in there?

The question was about Dropbox’s integration into the Finder — something Houston and Ferdowsi accomplished by hacking their way in. In or...