My $0.02 is that unless the coporations/governments put the kibosh on it like they're trying to do right now via onerous fees, Internet radio will outlast satellite radio. As VAX noted one can already access the net even whilst driving and I predict that eventually wireless Internet access will be available anywhere on earth. Add the fact that stations like the Moon allow one to request music and have a community with forums and chat for interaction and I'd say satellite radio is fighting a losing battle. Also virtual environments like Second Life are developing Internet access (including music and video) within the virtual environment so I foresee a time when people will gather in virtual "salons" and be able to chat using voice (if desired) and listen to music as if they were all sitting around together in someone's living room or sitting in a theater watching a concert.
http://news.zdnet.com/2100-9588_22-6186997.html