When the iPhone was first launched the story was told that there would be no local applications and that developers should build Web 2.0 solutions. Given that the first iPhone was limited to slow EDGE data rates, that felt like using dial-up modems back in the 90s, these sites had to be carefully designed to minimize the amount of data being shuttled back and forth. These limitations drove the creation of some of the best designed web interfaces.

A lot of users prefer them to the regular web interface as they convey the important information succinctly, without a lot of clutter.

Edward Tufte writes about the iPhone, "The content is the interface, the information is the interface, not the computer administration debris." 

Powerset CEO Barney Pell told John Markoff of the New York Times "The small screen forces you to be even more ruthless and focus on usability almost like a haiku".  

If you use a Site Specific Browser (such as Fluid or Prism) you can select your User Agent to report to the remote server that you are using a mobile phone, even from your desktop.

With billions of mobile phones in use, the future of web design is mobile.