1. Mobile phones these days are computing platforms. The reason why Microsoft dominates the desktop market is because the vast majority of software runs on it (hey, Macs are cool too, but they don't have the range of PC software). Apple's iPhone has already claimed that victory - to beat the iPhone, one needs to provide an easy way of uploading software, and, IMHO, a way of verifying the quality of the applications.
2. Apple has the advantage that it could leverage off the existing developer base for the Mac - that is, the development environments aren't completely different. Try releasing any computing platform in which people have to learn *another* darn computer programming framework/language and see how you go. Computer languages take *years* to grow to a critical mass.
3. Every technology marketer is saying "blah killer" at the moment. Can you honestly imagine the Palm marketing executives saying, "our phone is pretty powerful, but we really will have to see if the community adopts it and develops worthwhile applications for it". At the same time, all the little journalist worker bees have to get page hits in this new online news world. "iPhone killer" turns up constantly, because it gets clicks. Your here and I am here aren't we :-)