Where is that policy and discussion?
In terms of en.wiki...
http://en.wikipedia.org/wiki/Wikipedia:ELNEVERhttp://en.wikipedia.org/wiki/Wikipedia:ELNEVER#Restrictions_on_linking
That is the main restriction against external linking which makes an extremely strong (even for WP policy) statement; *"Material that violates the copyrights of others per contributors' rights and obligationshttp://en.wikipedia.org/wiki/Wikipedia:Copyrights#Linking_to_copyrighted_works should not be linked."* * * Specific guidance on YouTube (and related) is here:
http://en.wikipedia.org/wiki/Wikipedia:YOUTUBE#Linking_to_user-submitted_vid...
Which clearly just cautions care against using such links (*Links should be evaluated for inclusion with due care on a case-by-case basis*).
Policy discussion is best done on the relevant talk page. Although I seriously doubt that this is likely to be changed.
Tom