Great post from Gruber about iPhone apps running in the background. Here’s a tidbit I didn’t know. Makes sense:
The iPhone (and iPod Touch) only have 128 MB of RAM, and WebKit can use a lot of memory. When memory gets tight, the system sends low memory warnings to running applications, telling them to purge what they can. Eventually, the system will start forcing apps to quit in order to free more memory. That\’s why sometimes when you relaunch Safari, it remembers the URLs, but has to reload the content for all of your open web pages â€” that\’s what happens when Safari is asked to quit while it\’s running in the background.
Full article: Daring Fireball: In the Background