Actually the part about adding a mirror is not enough e.g
There is a 1.4GB movie, i rar it into a single link and then upload it to FSC and MU. Now as this is a 1+GB file free users wont be able to download from MU as well, so the basic purpose of a mirror is lost. They have to either buy a filesonic premium account or a megaupload premium account, and if the filesonic link is first, chances are they will buy that account. So the uploader wins and the downloader looses
I think a rule should be there that makes it compulsory for uploaders to upload files which are downloadable by free users, this way they wont be able to exploit the downloaders.