In a recent blog post, Craig attempts to explain why Apple will not be giving developers access to backgrounding services on the iPhone. He points out that in a mockup design of "Mobile Twitterrific," based on the jailbreak/community toolchain, refreshing the XML data from Twitter every 5 minutes led to a dead iPhone battery in only 4 hours.
"The heart of the problem [is] the radios. Both the EDGE and Wi-Fi transceivers have significant power requirements," he says. "Whenever that hardware is on, your battery life is going to suck."
He also reiterated what Apple said about the "Core Location" feature that Apple provided in the SDK: use it only on an "as-needed" basis. Craig said that the issue of backgrounding services may get addressed later on, but right now Apple is preventing iPhone developers from "shooting themselves in the foot." He said that it will take months before the desktop developers have gotten the mindset of an iPhone developer, and that thinking like a desktop developer will lead to bad designs.