There isn't one, the upload limit is 1GB and 10min. It compresses it to a smaller, lower quality file.
http://www.youtube.com/blog?entry=X--e2MeTQNs
The video frame size is scaled to
around 320x240 and frame rate to 25-30 frames per second.
Audio is transcoded to a lower bit rate and reduced
to mono. Other factors which affect streaming quality
include network conditions and server load.
YouTubes averages around 250 kb/s.
http://conferences.sigcomm.org/co-next/2007/papers/studentabstracts/paper28.pdf
It uses an algorithm that compresses from the total size divided by total time to determine quality and bit-rate. This is why they can put black screen time at the beginning or the end to make the video appear to be higher quality.
I would cite regulation, but I know you will simply ignore it.
