Swipe up vs Slingshot to close an app [webOS 3.x]
This tip is only for devices running webOS 3.0 and higher
Ever since webOS 1.0.1, you were always able to close an application simply by swiping the card off the top of the screen while in card view. When webOS 3.0 was released on the TouchPad, a new method of closing the application was added by pulling the app down to cause a "slingshot" effect where it would then fly up off the top of the screen. Other than the creating a fun Angry Birds slingshot sound effect easter egg, it did not appear has if this method was any different than just flicking it off the screen. However, as commented by webOS Developer Advocate Ben Combee in the webOS Developer Forum, it turns out that there is a difference for certain stock webOS apps.
For those specific apps, they are marked as "stay alive" to allow them to keep running in the background, even if you close the app by swiping up off the screen. This helps core apps like email, messaging, music and others to quickly launch when re-opened, but of course continues to also use up valuable system resources. It turns out that if you really want to completely close those apps, you can use the slingshot method.
To determine which apps are marked as "Stay Alive" you can load up Internalz Pro homebrew app and navigate to the "/etc/palm/" directory. Open up the "luna.conf" and "luna-platform.conf" files and find the "[KeepAlive]" section. According to my webOS 3.0.4 TouchPad, this includes the Phone, Email, Calendar, Messaging, Photos and Music Player apps.
Source: webOS Developer Forums