iPhone memory cannot be wiped clean even if you perform system restore. This is a bit concerning since selling a used phone on eBay to fund a new gadget has been a common practice to many mobile fanatics. More importantly, if you've ever returned an iPhone due to warranty, better hope the person buying it as refurb is not savvy enough to look up your personal data. If the memory on iPhones can't be wiped clean, its going to cause havoc for its users. Ironically, the more powerful this phone is the more it is capable to be used to access personal data. Knowing this, one would be better off destroying and throwing away an iPhone than to stay green and resell or recycle it for a good cause. That just ain't right. I sure hope in time, somebody will come up a software to help get rid of personal data.
Sources: Engadget and Gizmodo