I developed an infinite scrollview using Unity GUI, it was so painful, I'll never do this again.
And I was also looking for an infinite scrollview, but it could change the way the scrollview provides the scrolling.
Actually, the UIPanel is moving to the direction of the mouse dragging, and the clipping panel (if clipping is activated) is moving to the opposite way to "create" the visual effect of scrolling. I don't know how it can be modified to implement infinite scrolling. This is why, I guess, it's not yet implemented.