After a long battle with hackers who have been successful at jailbreaking the iPhone from one version of the OS to another, Apple is now taking a more personal approach to locking down the device. It's been reported that known iPhone jailbreaking/unlocking hackers have had their Apple IDs banned from Apple's App Store.
One of those hackers is Sherif Hashim, who recently found an exploit in the latest iPhone OS version 3.1.3 that could unlock the baseband version 05.12.01. Sherif now gets a message saying that his Apple ID is banned for "security reasons" each time he tries to access the Apple's App Store.
Baseband is the component that controls the connection between the phone and the mobile network; when unlocked, it allows the phone to work with any GSM carrier. Apple tends to release updated firmware for this chip specifically in order to relock iPhones that have previously been unlocked.
The exploit hasn't been released yet, though it has been confirmed that it works by DevTeam, a group of hackers that develop methods to jailbreak and unlock Apple's handheld devices.
Other hackers have also reported that their Apple IDs have been banned. It seems that this action of Apple's is merely a warning, as these hackers can always just create another Apple ID and access the App Store that way. It would be a lot harsher if Apple decided to ban their devices.