The iPhone platform elegantly solves the design problem of small screens by greatly intensifying the information resolution of each displayed page. Small screens, as on traditional cell phones, show very little information per screen, which in turn leads to deep hierarchies of stacked-up thin information--too often leaving users with "Where am I?" puzzles. Better to have users looking over material adjacent in space rather than stacked in time.
To do so requires increasing the information resolution of the screen by the hardware (higher resolution screens) and by screen design (eliminating screen-hogging computer administrative debris, and distributing information adjacent in space).
This video shows some of the resolution-enhancing methods of the iPhone, along with a few places for improvements in resolution.
For information please go to edwardtufte.com