It should be perfectly possible to run multiple applications on the iPhone in a way that protects battery life:  It could limit to the last 2 or 3, it could allow the user to specify which 1 or 2 is allowed, it could wake a certain apps every minute for 5 seconds, etc.  Allowing just 2 would make a huge difference in usability.

I get the feeling Apple is not allowing it simply because then they would have to allow iPod competitors to run in the background.   So they are just protecting iTunes, giving it another year to get entrenched.

This is a huge competitive advantage: Pandora and Spotify are just some of the excellent music services, but you can’t play a game or catch up on the news while listening!