One of the writer's colleagues noticed similar, with unpublished videos in their data pack dating back to 2008. A Facebook representative told Select/All that it was investigating the reason the old videos were resurfacing.
At the time, it seemed as if using Facebook's webcam recorder and discarding the videos that didn't pass muster would delete them. That certainly doesn't seem the case anymore. Problem is, if you recorded a video and didn't publish it, there's probably a good reason for it. That's to say nothing of videos (and photos) being far more intimate than the other forms of data Facebook sells to its advertisers. The videos are stored in the ancient .FLV format, which you need to use a media player like VLC to view.
How widespread this was, and if certain aspects of the practice are still in place isn't clear. We've reached out to the social network for additional information and will update this post should it arrive.