Who's to blame when someone loses their videos or has one of their favorite videos blocked that they can no longer see on Youtube?

 Barbara Streisand

if a video is blocked, it is usually because it contained copyrighted content.
in which case, it wasn't really THEIR video, as the content belonged to someone else.
like can you imagine just walking up to a car on the street and saying "that's mine". you would be breaking the law if you took it and did whatever you wanted with it. so why would someone think it was okay to take other peoples' stuff and upload it?