The design they describe is how you do anything on iOS that's going to go out and talk to some web services, otherwise talk on the network, or the like. You do

The design they describe is how you do anything on iOS that's going to go out and talk to some web services, otherwise talk on the network, or the like. You do your UI stuff on the UI thread and you use additional background threads for the network stuff. In any case, if you're not in the Facebook app, then iOS has frozen it and it's not getting any CPU time at all. Removing it from the multitasking tray does not stop it from consuming any CPU resources, because if Facebook isn't on the screen then it's not running.