I can't really agree with this actually.
I used to regularly post my work (not proxies, since I don't know how to get them myself) on other kinds of boards to share with people. I resigned from this, but it was not because of leechers at all. Actually leechers never really bothered me.
I think that even though 95% of the people who view posts never reply, the posters should share for the love of sharing. That's what makes a real contrubutor. He/she shouldn't care how the viewers act. Posting is all that matters.
Also, I don't consider people who reply with "thanks" as leechers. Leechers are those who view posts, but don't reply at all. They take, but do not give. Someone who thanks posters but don't/can't post their own proxies is not a leecher.
I don't think it's fair to ask for lists or contributions. I would assume that most people here don't know a thing about proxy-hunting, and even though they may want to share, they can't, or other things may be preventing them. It's not fair to penalize people who don't have the same skills as the posters.