Twitterific's author, Craig Hockenberry, notes that enabling background tasks for an iPhone version of Twitterific resulted in battery drainage in 4 hours.
The heart of the problem are the radios. Both the EDGE and Wi-Fi transceivers have significant power requirements. Whenever that hardware is on, your battery life is going to suck. My 5 minute refresh kept the hardware on and used up a lot of precious power.
This information provides some perspective on Apple's decision to limit background applications from running on the iPhone.
[ via Tuaw ]