What does this mean for copyright, fair use, and vids on YouTube?
Private companies like YouTube can take things down for whatever reasons they want, and they mostly claim to be complying with copyright, though sometimes it’s that they literally don’t want to bother to make the distinction between a fair use and just a pirated copy of something (likely to be less fair, though there are some arguments for straight copying as having some fair uses also). So most of the time, if you actually make a person see a vid, they agree that it’s a fair use: YouTube takedowns are mostly done by computer, now, and computers can’t tell the difference (or can’t yet: the EFF has made some good suggestions for reprogramming computers so that they can tell the difference between a transformative work and a straight up clip).