Microsoft reacts to other companies’ products. BlackBerry reacts. Samsung reacts. Google reacts. Apple influences. Apple releases what it thinks will sell and only if the product has a place among its siblings. An “iPhone Plus” doesn’t scratch an itch. Just because the Galaxy S III is wildly popular doesn’t mean a 5-inch iPhone is necessary in an already tight device lineup. And contrary to popular belief, customers aren’t exactly passing up Apple current offerings.

This is exactly why Marco’s story on the plausibility of the iPhone Plus didn’t convince me. “Everyone else is doing it” has never been Apple’s raison d’être. If Apple does this, and they might, the immediate pundit reaction will be “Apple’s playing catch up,” which is only going to hurt them worse than keeping up the existing iPhone form factors.

Damned if they do, damned if they don’t.