I'm glad to have come back to see this idea being discussed more
I agree there should be requirements. We'll have to check with Miranda what the post count ranks are(I forget-I think the first might be reached at 25), but having reached the minimum rank and posted a newbie thread sounds reasonable. This way, those who posted the thread are easy to monitor. In fact, it allows a thread to be made to "track" these new members' progress. Each time a new member makes a thread, they can be notified through a profile comment or PM that they were added to the new member list, this way they know we are aware of them and it might encourage them to stay a bit.
This could also fit into my mentoring concept, helping to identify people who may need help being new to forums or those who are having difficulty. This was more of a staff project, but new members could be assigned or request a forum mentor who will help them with issues, questions, concerns, and also provide a friendship to them which will help them become integrated into the forum. Its in the works(I've seen it on GLAM! for dolling, never quite as an actual forum posting business, though I think The Gathering had something like it at one point) and rough.