[yuvi]

Develop all you want for free: as long as you only want to run your application on a simulated iPhone. You can't load apps onto your own device without paying $100/year or jailbreaking. Heck, you can't even use XCode to compile an app for the iPhone (not simulator) without a license.

Anyway, an additional multitasking use-case is IRC and other apps where you're in constant contact with a server. With Colloquy, for instance, right now you need to setup a server to bounce off of or else you leave all channels every time you switch apps. Of course, this class of uses is one that you don't want running when the device is off or else the battery drains quickly.

I've always felt that Apple was waiting both for their hardware to become powerful enough (the original iPod touch consistently ran out of RAM with 2 open webpages + music for instance, and page rendering wasn't exactly snappy) and also to come up with a good way of limiting the number of background processes without user involvement. You don't want every other app you launch hanging around so that when you run out of resources, the OS kills the music player which you actually wanted open.