When developing for Android, you can set your target (or minimum) sdk to 4 (API 1.6) and add the android compatibility package (v4) to add support for Fra
One big thing all the above comments don't mention is that a fragment remains resident in memory even if Android kills the activity and restarts it when you do something like change the orientation of your device. This is done for performance reasons but can also lead to unexpected results if you were expecting fragments to be destroyed only to find that they are getting recreated out of nowhere.