A multi-touch screen, like a design for an airplane should be patentable. It actually takes serious R&D and discovers things that were not understood before. Obvious things you can do with multi-touch screen or airplane should not be patenable. Any programmer that had a multi-touch screen to play with would come up with pinch to zoom. Allowing pinch to zoom to be patented is like patenting aerial photography, an obvious use of an airplane.