Some forensic tools like Lantern 2.0 allow the use of a passcode bypass file to get around the passcode lock on iOS 4.2 and later. This means that if someone has your device they can get around the normal restriction to not sync until the device is unlocked.
I'm wondering which file or files iTunes creates and stores to convince a locked iOS device to sync over USB. Even better would be an analysis of the specific keychain items are needed to bypass the passcode lock for iOS.