Dev post on Wow forums today announcing the channel. (-And yes I see the join date on the channel, not sure why they waited but I tried to find one the other day and could not.)

World of Warcraft - English (NA) Forums -> Blizzard Entertainment on YouTube


Dev quote:
  • 0. Blizzard Entertainment on YouTube 09/30/2009 10:04:46 AM PDT


The new official Blizzard Entertainment channel on YouTube is now live! YouTube - blizzard's Channel

Check out high-quality streaming versions of our cinematics, gameplay trailers, and in-game movies. Make sure to come back often, as we will be adding even more video content in the weeks ahead.

Link: YouTube - blizzard's Channel