Ask HN: Why do some YouTube submissions get [dead]ed?

From time to time, I will submit an interesting YouTube vid that's pertinent to hacking. Such as this one about a guy who built an Oculus Rift clone from an iPad: http://youtu.be/4uUsctp3CJA These links are immediately marked [dead] yet from time to time I've seen other YT vid submissions sail through. Can someone explain why? I understand the aversion to turning into Reddit or MetaFilter, but I'm not submitting cat videos. If there had been a blog post instead of just the video, I would have submitted that link.