All iOS devices from the iPhone 3GS have a hardware encryption chip, right?
When you erase an iOS device with the "Erase All Content and Settings" menu item or via Remote Wipe the encryption keys are deleted. However, the data is still present on the device in an encrypted state.
Does this mean that forensic experts or perhaps anyone with the right tools can retrieve the data and decrypt it by other means?
Has Apple left a backdoor of some kind for law enforcement and security professionals?
As an aside there is an app called iShredder that claims to use various military grade wipe algorithms that can wipe your iOS device, but I don't see how this is possible as all iOS apps are sandboxed.
UPDATE: I know understand what iShredder does after Jonathan Garber's and Lucas Kauffman's comments.