direct sublink is: http://daringfireball.net/linked/2008/march#fri-21-jens

"Another one from the I-don’t-agree-with-it-but-it’s-well-worth-reading dept.

For what it’s worth, I believe the number one reason why the iPhone OS doesn’t allow background processes is RAM. Battery life, CPU sharing, bandwidth — all of these are factors, too, but I think RAM is foremost. The iPhone has just 128 MB of RAM and no swap space. A good chunk of that 128 MB goes to the OS itself and the built-in apps that do run in the background — Phone, Mail, Safari, and iPod. There really just isn’t much left over. If Apple were to just allow background processing now, what would happen is that background processes would often wind up getting killed by the OS at some point when the frontmost app needs more memory. From the user’s perspective, it would seem as though background apps inevitably mysteriously fail and stop running. You can argue that you’d rather have that than no third-party background apps at all, but it’s clearly a reasonable trade-off for Apple in terms of consistency and obviousness in the user experience.

Wait a few years for iPhones with 1 GB of RAM and it’ll be a different story."