OK - I've taken a quick at the videos posted in your permathread and see that a large number of the videos that you listed have been removed.

In some cases they are simply removed for "violation of terms" in some cases a copyright infringement is noted (and crediting the copyright owner) and in still others they've been removed by the person who owns the Youtube account.

I suspect that many of the clips that are up on Youtube are "bootleg" slips. Posted by some fan of the song or performer. These type of clips will always be transient on Youtube. Some composers will not be happy Maybe they just don;t want to be seen in that bad video, or were in bad voice that night - maybe they resent some using their song without permission. Record labels and promotion organizations will always guard their artists intellectual property fiercely - maybe just over protective, maybe they feel a need to guard their sales strategy.

And people who post the videos sometime just want to take them down, or change them or maybe the artist asked them to take them down (I have to admit, some of the videos other people posted of me are not ones I would have put up - but refrained from asking them to remove them and am thnkaful for their enthusiasm).

Anyway - I suspec you've been frustrated by the temporary nature of the Youtube video library - and the unsanitized way the videos are allowed to be posted (ie lots of inappropriate vids will get up, even good ones that we like - but that have not been properly permitted).