The problem with sites like this is that they rely on the artist contacting them and asking them to remove the album. The same technology which makes it easy to copy and distribute the music also makes it easier to track down and contact the copyright holder. If these sites would make the effort to get permission before putting albums up for download a lot of these problems would disappear.

This would then leave a small number of albums which it is reasonably safe to assume will never be re-released, and there may be a moral case, if not a legal one, for making these available for posterity.