Why the hell would anybody pay for radio? I live in Minneapolis and I only listen to a couple local stations anyway, much less have a need for stations all across the country. Most of the music that I want to listen to is already on my iPod. Think about it, does anybody know of someone that consistantly uses the Radio section of iTunes? Probably not.
Remember that Jobs is dead on by saying that people want to own their music not rent it (like services Napster, Real, etc). This directly applies to satalite radio because it would, in essence, be another variation of the "renting" music philosophy. People want to play a particular song or CD over and over and have control over when they want to listen to it, not every blue moon. This is probably why the new iPod Shuffles have both repeat playlist and shuffle options.
I look at it this way:
iPod - $400 - $500
iPod accessories - $100 minimum
average iTunes Store downloads - $50 - $100 annually, (I'd assume)
XM/Sirius subscription - worthless additional charge.
I might be "cool" to have this feature on your iPod, but it's unnessisary for the majority.
A Sirius Apple iPod Would Be Seriously Cool