Jakob Nielsen, the Danish web usability guru, has been looking at the state of the web for mobile devices. He compares it to the desktop web of 1998
For the best user performance, you should design different websites for each mobile device class — the smaller the screen, the fewer features, and the more scaled back your design.
This is a great point. You’ll see, if you request a page from my site on your iPhone or iPod Touch, that the page will be rendered in an iPhone-friendly format. I’m using the WordPress donationware plug-in WPTouch.