Warning: iPhone "Restore" does not delete personal data! - From CNET
So don't leave your personal information vulnerable to identify thieves. Ensure it's not recoverable by permanently wiping the iPhone 5 with SafeEraser. When got a new iPhone 5S and want to resell your iPhone 5, you should watch this video.
iPhone Data Eraser
> Permanently Wipe All Personal Info from iPhone, iPad & iPod
> Erase Traces of the Deleted Files on iPhone, iPad & iPod
> Works with all iOS devices - Jailbroken & Locked iPhone