Fwiw, one of the (groups of) videos that I noticed was missing was the Frank Rosolino "Jazz Scene USA" performances that have been commercially available. However, I had also noticed the disappearance of a bunch of videos uploaded by a jazz guitarist in Holland that I'd been following. That could be coincidental to whatever else may be going on, I suppose. Never having uploaded myself, I wonder if there are limitations to the number of videos one can upload.
Also, after viewing one of the videos by this guitarist, I noticed that there was some sort of automated display of samples (some were directly related to the video I had watched, such as other guitar players playing the same tune; and some were not only completely unrelated, but shockingly so- such as a "lesbian kiss" video ) which immediately followed. Strange.
As far as searching, I'm not sure, but I'm not aware that you can do "advanced" types of searches (hopefully that will come). I just hope they don't screw it up completely (you can still search using quotation marks for specific phrases, unlike some other sites).