A "Leecher" is a individual who takes it apon them selves to try and mirror large section of the internet on their own hard drive for their own benefit. They download prolific amounts of data with out giving in return hence the name Leech, as in any aquatic bloodsucking or carnivorous annelid worms of the class Hirudinea.
That's not really mirroring. Mirroring is usually taking everything from a site, not the stuff you want--and it implies having it available for others. The second sentence is pretty much it. Reminds of upload/download ratios back in BBS. Problem is you get people uploading crap (blank or corrupted files).
Some P2P services sutch as eDonkey2000 work around this problem by having people have an automatic up/down-load ratio. Another way of limiting leechers is by just kicking people off of your server when they don't share.
Is there any difference between Leechers and Leeches? Perhaps the two pages should be made into one, and redirection used?