I am strongly opposed to imposing a limit on downloading resources. The goal of our contributors (or at least the majority) is to freely and openly help others so that they receive a better education. We don't ask for anything in return, because we ourselves are repaying the debt we owe to FSN/VN/AN when it helped us immensely in our year 12 education. It is in this spirit that FSN/VN/AN has grown, that we give first, then hope it has made enough of a difference in the members' schooling that they feel compelled to give back to the community. This very philosophy is admirable, and I hope it will be in this spirit that AN will remain.
That and, the resources uploaded are at the courtesy of the uploader. If we were to restrict the accessibility, that is the discretion of the uploader, not the discretion of ATAR. I think many uploaders will agree to keep it unrestricted.
I have also been on sites where there has been a post limit on downloading. It just means the off-topic boards will be flooded constantly with crap so people can quickly get their 50 posts. Mods can try to stop that, but then new member uptake will drop very fast, essentially restricting the place to a handful of long-term members ('elitist', as iamtom put it).