That design has a couple of problems. Most of them involve preventing accidental scrolling while allowing intentional scrolling.<p>Walking can cause accidental scrolling. Have you ever tried to hold a pan of water while walking? It sloshes forward and backward because humans don't walk at a constant speed. Every step is deceleration followed by acceleration. Any vehicle changing speed can cause accidental scrolling. A car accelerating or braking, a bus making stops, a subway. Fine-tuning the code to detect when to scroll would be a nightmare. If you make it less sensitive, users will complain that they have to tilt the phone too far to scroll at a decent speed. If you make it more sensitive, users will complain that it scrolls when they're just holding it.<p>It's not as intuitive as touch scrolling. Tilt scrolling requires "zeroing" the phone and being very careful with how you orient it. Touch scrolling is simple: text on the screen moves with your finger. With touch scrolling you can flick your finger across the screen to start scrolling far/fast, then touch the screen to immediately stop scrolling. You could copy this behavior by allowing touch and tilt scrolling, but then it gets even less intuitive.
I think tilt-scrolling would be quite unusable, albeit a nice optional feature - would be nice to play with it to see if it really works. There is definitely a problem with scrolling on the iPhone when it comes to long pages - making scrolling to the bottom of a page pracically impossible in some scenarios. There is this bias towards scrolling to the top, but not the bottom embedded into iPhone's design. That's why I made the End Of Page app for Safari on the iPhone - it lets you scroll to the bottom of very long pages without having to flick forever. It is free - I am releasing it in the hope that others find it useful. I should be on the App Store on Friday, provided all goes well with the approval process.