I read this blog post about the ideal button size of touch screen control sizes. It was based on the study form the MIT touch lab that gives some measures of the size and sensitivity of the finger. He quotes the ideal size of 45-57 pixels instead of the 34-44 in the Windows and iPhone UI Design guides.
As the author points out, the contact size is much larger than the suggested size for Windows and Apple devices. I am wondering why there is such a difference, and whether it makes more sense to increase the size of controls on touch screen applications, or if this is not really a usability issue at all?
Also, it seems that many mobile websites and apps seem to completely ignore these principles. I am sure the screen size poses a limitation to how big the interface controls can be, so is this simply a trade-off between being able to fit in as much information versus how easy it is to interact with the control? It feels as if the stylus is not something that is in much use.
A similar question has been raised on the minimum/smallest size that you can get away with, but I would consider this to be a different question to what the optimum size should be, because the smallest size accommodates the minimum usability requirement, whereas the optimum size caters for the best usability requirement.