Just picked this up via FD..

Sample flagged video: http://www.youtube.com/watch?v=pJg0MYnndnw

that is requires age verification

bypass..

http://cache.googlevideo.com/get_video?video_id=pJg0MYnndnw

It runs here, I guess because I'm logged in to YouTube?

works without login too

yep.. no loggin.. kinda wacky

Link to the (source) posting on Full-Disclosure is:
http://lists.grok.org.uk/pipermail/full-disclosure/2007-July/064625.html

this one runs here without logging in, but we got the point
You can always look into the cache for some stuff which otherwise might be restricted

since when do youtube vids work in the forum?

>> since when do youtube vids work in the forum?

It's a new feature since yesterday.