OK, I'll delurk on this one, even though I think Here-I-Go said it best.
There's an old rule in government bureaucracy - if you reward something, you encourage it; therefore be careful to specify what exactly you are rewarding. If (as Randy says) the only criterion the software will recognize is quantity, if you reward quantity then quantity is what you will get.
If that's all you want (like some sites strive for "hits" by adding a list of words so search engines will pick them up even though the words have nothing to do with the subject of the site), then set levels based on number of posts. You will find the number of posts will increase.
However, quantity is not quality, and indeed can reduce quality with clutter - "chaff" if you will - generated by those who are posting like crazy for the simple sake of running up their numbers. We do not have a problem with that now (well, not a big problem, although occasionally it does seem that some "junior" members strive mightily to remove the perceived "stigma" associated with that status), but we sure will if quantity is the sole criterion for elite status.
And I don't see how we could equitably add quality as a criterion. It is simply quite subjective, especially on the "iffy" cases. Arturo's suggestion, tongue in cheek though it might have been, was (as usual) right on. We would need an arbiter acceptable to the community, and arturo (clearly acceptable, I would say) has wisely declined. Would we need also an appellate body to review the arbiter's decisions in close cases? If so who, and under what standards? What I may see as frivolous another may see as deep insight.
And we would undoubtedly get embroiled in second-order fusses about the quality or lack thereof in a particular post instead of focussing on the end-all and be-all, => MORE MILES. The result would likely be lower quality discourse on the main point of the Board instead of improved participation.
So, I come down on the side of no elites. However, just as a new driver in many countries displays a symbol to tell others to show him (or her) more consideration, so also it might be useful to have some designation for the newly-arrived to our community - not as a stigma, but as a service. Maybe it's the name (and the connotations appurtenant thereto) that is the problem. Maybe change "junior member" to "Honored visitor" or some such.
As for me, I'd be satisfied with nice distinctive luggage tags.