With the release of Firmware version 1.1.1 for Apple iPhone (Update),renders them useless, unless you are willing to get an AT&T contract. Installer.app and any other unlocking associated software is rendered useless by the update, as well. It is still in the stored on the phone, but the application will no longer appear on the screen. Further, the update puts unlocked iPhones into the Activation screen that awaited normal users when they first purchased their phone

Apple released a statement earlier this week that, “Apple has discovered that many of the unauthorized iPhone unlocking programs available on the Internet cause irreparable damage to the iPhone’s software, which will likely result in the modified iPhone becoming permanently inoperable when a future Apple-supplied iPhone software update is installed.”