That was just an example of a hardware failure where the iPhone could not be restored. Everyone seems to like to say "It's always restorable if you want to bring it back to Apple..." well, not always. The fact is, it voids your warrantee. I don't give a crap about jailbreaking or not jailbreaking anymore though. I personally, grew out of jailbreaking and with 3.0 fast approaching, I think I'll be more than spoiled with great features that the jailbroken versions can't even touch.
Again, jailbreak doesn't require to replace boot logo.