It’s not often you get a radical change in the WIMP model, but the mighty Christian Giordano has tried just that with the introduction of “overlay scrollbars” in Ubuntu 11.04. Unfortunately, I think this is what might be called a “misfire”. The main problem is that in hiding the thumb of the scroll bar by default, you are immediately up against Fitts’s Law because the reduced size of the target will slow its acquisition. That’s an HCI fail – and …