Apple doesn't document how their iphone touch interface works. I have to use google to tell me how to do things. I don't want to have to use google while driving to figure out what the interface is.
I've been designing user interfaces my whole professional life. A "majority" isn't good enough. Especially when operating a machine going 60 mph.
Consider the key fob to my car. It has two buttons on it with icons - lock and unlock. You'd think that's what it does. Not so. It has all kinds of behaviors based on how you press the buttons! Thinks like setting of a siren (which won't turn off until you put the key in the ignition), opening all the doors or only one of them, opening the windows, putting the car in "sentry" mode (whatever that is), etc.
I also got to wondering why the battery in it never died, like it would do in other key fobs. It turns out it recharges when inserted into the ignition lock! (I actually kinda liked that feature!)
