[jerf]

I don't have an in to Google, but a bit of fairly simple logic would suggest that while YouTube presumably puts the short tail of popular videos on all nodes, the long tail will be much more distributed and less replicated; the costs inevitably force them that way. I can't prove it but as a long-tail consumer myself I believe I've witnessed some videos getting pulled in from some slow long-term storage before, things like conference videos from five years ago in the low hundreds of views.