Agreed. A killer app would cause many more people to want to buy the iPad. It would transform the iPad from a want to a need.
From the post:
But as platforms mature, Killer apps from third party companies pose more risk.
Is this really thought out? Does the Killer App transform the hardware into a commodity device for running the app? Is there some fundamental law saying Photoshop had to rule over all image editing? I don't think so. It's not Killer Apps that are dangerous. It's 3rd party monopolies on vital parts of the ecosystem! If Photoshop had better competition so it did not become a de-facto standard Adobe would not have been a threat. If Internet Explorer and Microsoft Office hadn't totally dominated their market niches, then those applications wouldn't have been a threat to Mac and OS X either. The Metroworks IDE has already been mentioned on this site as well.
I don't think Apple wants to eliminate killer apps or good apps. I do think that they want to ensure there is viable competition. It's not a killer app on their turf that Apple fears. It's someone else's monopoly!