"What I discovered is that... as a subscriber... you get the fancy interface thingie... THIS DOES NOT REGISTER A QUEST COMPLETION!
You gotta click the comments link to have the "real" page come up rather than the half video half other videos view. This should net you your prize (and you don't need to watch the videos... I don't think...)..."
This is from a Quests hint thread. Never had any luck with any video quest.