We've had a few TiPb readers ping us to ask what's going on with timeline-based apps like Twitter, IM, RSS, etc under iOS 4 multitasking -- specifically why they aren't updated or updating any more when they open. The answer is the current timeline update conundrum.
First, it's important to remember that Apple didn't include background timeline updates in their multitasking API. Apps can stream music, they can wait for VoIP activity, and they can handle location for navigation or check-in, but they can't update your Twitter, IM, or RSS the way Apple's own Mail app can. Apple's SVP of iPhone Software, Scott Forstall said they prefer iOS handle that via push notification instead.