In 2009 I built T-Mobile’s YouTube brand channel. You can see the first version of that app in this video:
In the second version of this channel, however, I added all of the YouTube sharing features into the Flash itself, so you could comment, rate, share, favorite, etc, right from within the SWF. Needless to say it involved some intense YouTube API integration. At one point YouTube was showing this channel around to clients as an example of what could be done with their brand channels. I just wish I’d captured a video of it in its final state, since it’s no longer in use.