I'm sure you're more than willing to help out in this regard, too!
I've never banned a member for failure to use the search feature, and in my time here, I can only think of about 3-4 members that were banned because of it, but their
New Thread Creations-to-
Contributions in Existing Threads ratio was very high (say, over 10), and they became extremely defensive when asked to change their ways or use the search engine.
If I know the game (so that excludes GT5

), I'm usually willing to help out, but now that I can lock threads, it's a different matter. If some thought and work is put into the said post, I'd personally rather merge the post/thread into another thread.
Some people create threads with totally ambiguous titles, which is probably my biggest moderation pet peeve of all. You see them, they say: "How do you...", "Quick question...", and of course "GT_ question". If it's actually a topic or question that hasn't been discussed, and there's lots of responses, then there's the process of concocting a title for it.
Or the discussion splinters off because someone asked a totally different question within another thread, and it takes off from there. That's natural, in a way, and it sometimes shows the vitality and experience of our community; and that's something that's a lot more difficult to police. Sometimes we encourage it, and other times, we do not (some discussions go in a bad direction like name-calling or politics, and/or steer far away from the original topic and context of the sub-forum).
There's no absolute rule for this, since we are seeing that members are tending towards contributing towards these all-in-one threads that go on for 500 posts or more. It's only when it becomes an unmanageable mess that we say something. Personally, I'd rather there were new threads for a separate discussion, rather than an ongoing thread that gets away from itself. But that's not my call to make.
Of course, careful what you wish for...I can't imagine the barrage of new threads that are going to fling in all directions once GT5 arrives in stores, but we moderators will be very busy in the queue.