In truth, I knew about that for a while, actually. Research shows that they are put up by the original studio that produced the films. A number of them are movies that are so old that they are either rare or can't be found anymore. So for big time nostalgic fans, it's a nice treasure.
And it's not just movies. TV Shows are also getting this treatment. The original owners are putting them up. I just love finding these old movies and videos.
BTW, the TV Shows can be found here:
http://www.youtube.com/showsNote that they also have put up Anime. Too bad it's only the dubbed kind. So, unless it's done by a company that keeps it in tact from the get go, (ie Funimation) you can pretty much expect crap from that. -_-