It appears that there is a misunderstanding on how iOS handles multitasking. Thanks to Fraser Speirs we now have an extremely detailed report on how it works and what the multitasking bar actually does, or doesn’t do in this instance.
Advice handed out by some people is that you need to kill the apps in order to free up memory. While this can be correct in some circumstances, generally you need to do nothing to preserve the available RAM on your iOS device.
If memory is becoming scarce, iOS will automatically move Suspended apps into the Not Running state and reclaim their memory.