Joe: Apple's solution for notifications on the iPhone is just really crappy; I just can't stand those modal alert boxes [page 276]. When you're using an app and a notification pops up—this happens to me all the time when I get text messages—you go to tap something, and whoops, you just accidentally tapped on a little alert that popped up instead. Even worse, these alerts force you to pay attention to them right away. You can't scan them and then go back to what you're doing. If you get more than one message, it just groups them and says you have two, but you can't read them. There's no way to just easily scan messages—they take over what you're doing and demand your attention. But if you want your app to offer push notifications, you have to do it that way.
Within the app itself, though, I could be more subtle. When you get a notification in Facebook, it appears at the bottom of the screen; it just slides up from the bottom. I actually based that on notifications in Palm's webOS. Palm really nailed it: when you get anything important, it shows up in a very thin line at the bottom of the screen with the content. You can tap it to act on it or you can just swipe it to get rid of it. That's what I tried to recreate in the Facebook app. I like those challenges where I have to go the extra distance. That's the fun of it.