Considering Nintendo has been doing a ton of touch based gaming with the DS for all these years I don't really see that being a reason investors would be nervous.
Considering the strong words Nintendo had for Apple in the past I get the feeling this is their reaction to the popularity of the iPad, iPhone (and touch based gaming in general). So instead of being revolutionary like the Wii they are now reactionary like the PS Move & Kinect, this could be the reason investors are…
I dunno... I think the controller has people nervous. I think thats what was behind the drop in Nintendo stocks. One, its expensive. Two, the Wii has a big kiddy market, I imagine parents will be concerned about handing their grimy accident-prone kiddies such an expensive controller.