With iOS 7, Find My iPhone includes a new feature called Activation Lock, which makes it more difficult for anyone else to use or sell your iPhone, iPad, or iPod touch if you ever lose it. It starts working the moment you turn on Find My iPhone in iOS 7.
With Activation Lock, your Apple ID and password will be required before anyone can reactivate and use your device
Activation Lock is enabled automatically when you turn on Find My iPhone in iOS 7, or when you upgrade to iOS 7 from a previous version of iOS that has Find My iPhone already turned on.
When you enable Find My iPhone on your iPhone, iPad, or iPod touch running iOS 7, the Apple ID and password you use for iCloud is securely stored on Apple’s activation servers and linked to your device. From that point on, your password will be required before anyone can turn off Find My iPhone on your device, erase your device, or reactivate and use your device.
To turn off Find My iPhone on your device:
1) Go to Settings.
2) Tap iCloud.
3) Sign in with your Apple ID, if necessary.
4) Turn off Find My iPhone.
For more information about this topic, please visit http://support.apple.com/kb/HT5818