It seems the site linked to has been served with a take down notice and has complied so it seems there is no need to remove the links, I think there is a case for mashups but only when they are of limited time or use small samples as otherwise artists works would be open season for anyone at zero expense and much as I don't like the selfish recording industry I do feel its fair that an artist who has done some work gets paid a royalty for it and it seems those who make "underground" mashups don't offer a percentage to the artist or negotiate with the label etc, just going ahead and using the work in this manner is the same as just disregarding the owners rights and we all know where that leads eh folks.
This is a shame really as some mashups are excellent but in a world with over-extended time periods on copyright it seems some things are not meant to be and creativity is often one of the first casualties.
When copyrights where first thought of the law was to protect the composer of the work for a limited time, and was originally about 10 years, now its anything between 50 and 150 years depending on which industry bribes their politicians most effectively to monetize what should be works in the public domain, remember that when your paying out for old music, in a fair world it would already be yours for free.