I too voted "yes" but I imagined that the iPhone programming would be a subset of "iPhone" rather than a separate "child forum" of "Mac Programming."
I thought that those who would be interested in discussing iPhone programming would most likely head to the iPhone forum first since using an iPhone is not inclusive of using a Mac.
"iPhone Programming" is, however, extremely similar to Cocoa development and is not open to development using other platforms. That is, unless you use the toolchain, but toolchain-related questions have been few and far between so far which means that iPhone development is exclusive to Macs for the most part.
I don't think it should be a subforum at all, but if its going to be subforum then iPhone is definitely not the place for it.
kyre: The threads on the FIRST page on Mac Programming go all the way back to last Thursday. Subforum splits are usually reserved for extremely high-traffic forums, like iPhone or MacBookPro/MacBook used to be. I don't think Mac Programming simply has the volume to support two separate, distinct subforums without having an adverse effect on both sides on the divide.