Interesting paper on the size and scope of Youtube videos:
Dialing for Videos: A Random Sample of YouTube
And a site with tools and summary data on youtube:
tubestats.org
Got the above links from this video:
Dialing for Videos: A Random Sample of YouTube
And a site with tools and summary data on youtube:

TubeStats
TubeStats is an open-source tool that lets you navigate YouTube data and compare videos across the platform.

Got the above links from this video: