How can I completely erase all personal data from my jailbroken iPhone?
Chances are if you're returning your iPhone or considering selling it in order to upgrade, admist recent reports of refurbished iPhones still containing personal data, you are going to want to do everything you can to insure your iPhone is as clean and clear as can be.
Thanks to a recent article on iPhoneAtlas, you can now take extra steps to protect your personal information. These steps require a jailbroken iPhone, and are outlined as follows:

