I’ve only glanced at the Android developer guide, never thoroughly read it. Which I’m doing now. I’ve just started so don’t get your hopes up. Never the less, just after reading a few pages I’m already impressed. The guide is easy to overview, and it thus far remains the best API documentation I’ve seen so far.

One of them is the following passage:

By default, each application is assigned a unique Linux user ID. Permissions are set so that the application’s files are visible only that user, only to the application itself — although there are ways to export them to other applications as well.
Just look at it, it’s. So elegant, simple, yet it solves a lot of problem by using simple convention and the tools available in the operating system.