They are and there's old firewalls out there that report Youtube traffic as a UDP DoS attack.

Youtube will at the very least fallback to HTTP over TCP for watching (no idea about live streaming).

I did a lot of funky things to get around the "drop all UDP" firewall at my first student dorm :)

nope, https from https://rr6---sn-xxxxnel.googlevideo.com/videoplayback?expir... ......&sig=xxxx&lsig=xxxx&n=xxxx either mp4 or two separate audio/video streams