Triumph of the Default
The privilege of establishing what value the default is set at is an act of power and influence. Defaults are a tool not only for individuals to tame choices, but for systems designers — those who set the presets — to steer the system. The architecture of these choices can profoundly shape the culture of that system’s use.
Kevin Kelly
I very much like the idea that the default behavior of a piece of software will dictate the culture that springs up around that software. Given a large enough audience (say, Facebook) those defaults impact the culture of a whole society.
So keeping that in mind, it’s terribly obvious how important sensible defaults are. Imagine you have no Settings screen at all, that the defaults are written in stone, and design as appropriate.