Didn't El Jobso address that at the WWDC? Wouldn't applications that "required" running in the background be able to utilize Push technology, instead? So that instead of constantly checking for new messages and destroying battery life, messages would be "pushed" to the phone instead?
I could be phrasing it wrong, but I think this was Jobs' solution to applications wanting to run in the background...
I think he also said that wasn't going to be available until September so I guess you'll need to have AIM open to use it.