There is a pretty serious flaw within iOS 7.0 and 7.1 that makes it near impossible to recover a stolen iPhone if the thief knows about the flaw.
Essentially all you do is press the toggle, which is next to Find My iPhone, and the Delete Account button, which is the iCloud setting, at the same time and then turn off your phone. The next time the phone is turned back on, the thief can then take away the iCloud account without having to use a password — essentially making Find My iPhone useless.
Of course, this flaw will only work if you don’t have your iPhone protected by a password or pin because the thieve needs the ability to use your phone to trigger the flaw. However, many iPhone users do not protect their phone with a password pin, though it is an important thing to do since iPhone have become one of the most sought after items by thieves.
YouTube user Miguel Alvarado has posted a video that shows the flaw in action: