This tip may prove useful to some. Forum user, technocoy noticed that the Safari on the iPhone intercepts a double-finger scroll differently than the usual single-touch scroll.
One issue for some web applications, including David Cann's iPhoneChat (iPhone Link) is the inability to scroll framed elements. In iPhoneiChat, this means users are unable to scroll long buddy lists with a simple finger drag. However, if you apply two fingers and scroll upward, the buddy list scrolls appropriately.
Per Ajaxian, Joe Hewitt has been trying to capture this event and has posted a small demo page which shows that you can drag an object (vertically only) with the double-finger scrolling on the iPhone.
Meanwhile, through some of the efforts involved in hacking the iPhone, there has been evidence that the iPhone may support up to three finger events. One event is named "tripleFingerGestureTriggered". All documented iPhone mutlitouch functionality to date has been limited to two discrete points.