Well, it's not limited to stylus v. finger, as you may want to switch views for other reasons. This happens all the time and may also be desirable for reasons as yet unthought of. Instead of binding a hardware key to the functionality, the hardware key and its binding should be a part of the UI and then app should provide the functionality. In some apps (media player) you may want different view switch than in others (such as PIM).
i keep wanting to use the [menu] key for exactly that. a great number of input dialogs would go well with a simple/intermediate/complex UI option, just cycle round them. also there is the Code/Design/Run cycle that the on device IDE should have..