Well, on the iphone when it want's to tell you something you get a annoying Pop-Up completely interrupting whatever you're doing.
Android, and webOS has much nicer notification systems. Android has a notification slide-out bar which slides from the top status bar.
& webOS, (Which I think has the best Notification System) give you notification from the bottom, and tap on it to open it (Msg, or whatever) and if you don't want to open just ignore it.
Edit: sp