Well, we currently have the problem, that we can restore our iPhone 3GS only to the 3.1 firmware, for which there is no jailbreak available currently. It seems, there will be a jailbreak for 3.1 soon.

But what, if an iPhone got stuck somehow and can only be revived with a firmware restore via iTunes? If the baseband would be flashed to a current version during the restore, the iPhone likely would be locked forever.