It has been awhile since I've gotten a chance to loop back around to this thread, but I have to disagree with what you've said here. The Necro-posting inevitably provokes those threads to be a part of the spam problem. If they had been locked prior to the necro-post, then the spammers would not swarm into the thread. It is a domino affect in many cases, where a necro-post, due to a lack of locking the thread begins the cycle of spamming the thread endlessly. I think the auto-lock feature would help with quite a lot.