I have looking in Google to see if there will be a way to have Linux running in your iPhone, and could not find a way yet.
Anyway considering that you can run Linux on an iPod it is supposed that will also be possible to have it installed on the iPhone.
As it will have a lot of software features as this article show, iPhone features I found myself thinking how the cellphone is going to work if you decide to format your iPhone and install Linux on it.
Maybe the software that will manage the phone will be embedded in a ROM (Read Only Memory) and the OS X will only be used to run all the other applications such as Safari, the Google Maps or the email client that iPhone will have.
Well I think in the near future we will know how to do it, anyway we (The Linux Users) always do!