I think the real reason Apple doesn't allow third party apps to run in the background on iPhone devices is because Apple doesn't want third party apps competing with it's own solutions. By only allowing their own apps to run in the background it gives any Apple app an inherent advantage over a third party app. The bottom line is Apple doesn't want you running Pandora in the background and possibly competing with iTunes for your music needs. Also what comes into to play is the fact that Apple does not want these devices to be mobile computers, instead the Apple model for the iPhone, iPod touch, iPad is more along the lines of a specialized media consumption platform instead of a mobile computer. It's basically much like the game console model but more far reaching. In conclusion I don't see multitasking coming to iPhone OS soon because it conflicts with their business model in my eyes.