During my Introduction to Computer Concepts (state mandated high-school class), we were shown a rather dated CBS (I think) documentary on the iPhone, what made it so influential, and how were developers building apps and submitting them to be reviewed. The DVD documentary was published after Apple reached its 1 billion app mark.
The company submitted an app that had to do with "enhancing communication" (don't fully remember), and proceeded to run advertisements in anticipation of their app being approved quickly.
However, a group of indie developers got lucky that their app was approved within 3 months.