To set the scene, everyone knows about the iPhone. Everyone's super-excited about the App Stores - users and developers alike - and all its possibilities. Apple's competitors have taken a lot of ideas from the iPhone, and mobile operating systems are all the hype these days (that includes netbooks). As far as I'm aware, the N810 runs Android, for which applications are written in Java.
When I first saw the title of Matt's article ("Why no iPhone support for Firefox mobile beta?"), I thought, Why is this question even being asked? First off, it's obviously going to be a competitor for Mobile Safari (which Apple won't even allow in the app store ), and Firefox's not that fast of a browser, either, in my opinion, compared to Safari. Besides, all iPhone applications are written in Cocoa. Let's see Mozilla trying to rewrite all of Firefox, its plug-in architecture, its support for themes, etc, all in Cocoa Touch. Furthormore, quoting directly from the article, one of the many other reasons that Firefox won't be available for the iPhone any time in the near future is because "it [has] to do with restrictions on run non-SDK code[.]"
Not only that, but it would also provide two completely different SDKs for software developers to chose from: the iPhone SDK and whatever Firefox plug-in developers use. This is really dangerous for Apple. Apple wants in no way for there to be an alternative development SDK if not that of the iPhone - that's why Flash isn't on iPhone, and won't be, either. If a developer prefers Mozilla's way of doing things and wants to target iPhone owners as potential users, there would be a visible drop in terms of iPhone SDK developers and, hence, Mac users (and possibly the number of new Mac developers too).
All in all, Firefox on the iPhone is a really bad idea. Although, idealistically, it sounds nice, Firefox won't be able to live up to its "I'm a fast and customizable browser" promise.