YouTube limits for private videos?

Hello
As you all known YouTube its a video sharing site that allows user to upload virtually unlimited number of videos.
However, can YouTube be used as some backup service for videos?.
Could someone, for example, upload thousand of videos and keep ALL of them private and none public? assuming that video’s content doesn’t break any YouTube’s terms of service (no copyrighted stuff, no porn videos, etc.).

I already posted this question on Google’s product forums and the answer I got wasn’t exactly clear “YouTube its a video sharing platform not meant for backup or personal use purposes”, but on the other hand nobody said that isn’t allowed to upload thousand of private videos.
So I’m pretty puzzled right now, can such activity be considered as “unproper” usage of the service ? (and ultimately against the terms of service).