You don't have to defend it, the iPhone (must also include iPod touch) is officially in 2nd place behind the Nintendo DS.
The risk is that games will be further dumbed down to accommodate people who only have touchscreen interface. Consoles have already made some PC games frustrating to play because they removed the mouse based control.
It's easy to fix... the software companies should force people to buy a trackball or gamepad peripheral in order to play. It's a PC and also Amiga tradition of forcing someone to upgrade in order to play your new bells & whistles game.