One irritation I have is when the phone **bleep** apps to sleep, which in itself is a good thing as it helps reduce background usage etc for apps not being used
The problem is if you need the app again it involves some messing around finding the app and displaying the icon again which disappears when put to sleep or because there is no icon you forget it's on the phone and go to download it again
My suggestion for when apps are put to sleep would be to leave the icon in situ greyed out and when you click the greyed out icon it wakes up the app and makes it active again.
The main benefit of leaving a greyed out icon in situ would be a constant reminder to the user that the app is there and can help the user determine if the app can be removed to clear clutter etc and of course a very easy way of waking up the app if needed
Just some thoughts