Disney is perhaps best known on YouTube for clever fan mash-ups and Hannah Montana videos. Riding this wave, Disney's theme parks division figures a little impromptu singing and dancing on its well-groomed Main Street, U.S.A., will create yet another "magical moment." But winning over YouTube critics takes more than a happy song as Disney learns.

Title: Disneyland Musical Marriage Proposal

Stats: Appearing on June 8, this video has attracted more than 265,000 viewers and over 3,600 text responses.

What you see: A couple are walking along a crowded street in a Disney-designed downtown when the man steps forward, whips out a megaphone, and asks his girlfriend to marry him. She just shrieks and holds her hand over her mouth as he goes into a full song-and-dance routine of wedded bliss. She says very little—just an "Oh my God"—and seals the proposal with a kiss. A happy ending. The crowd cheers.

Take Out/TakeAway: T-Mobile drafted the blueprint for viral videos with its flash-mob dance routines set in London earlier this year. The number of copycats that have followed would suggest this take-the-crowd-by-surprise element will be a common feature of ad campaigns going forward, at least until the next big-buzz idea succeeds it. Evidently, Disney didn't get the memo, with a very obviously staged dance routine and marriage proposal.

Social Media Effect: Talkability is key to any viral video. And Disney sure has accomplished that, generating an active back-and-forth dialogue between fans and detractors of the "Marriage Proposal" video. The more critical YouTuber is vicious in his criticism, as one viewer writes, "asking her to marry him after ONE year? wow. idiot." But there are romantics, too, who are more forgiving. "They probably practiced it with somebody else but I dont think it was fake," another viewer comments. But the genie is out of the bottle. The fakery charge has been leveled.

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YouTube BrandWatch is The Big Money's exploration into how the world's best-known businesses, so adept at managing their images offline, are being perceived online, where control is harder to come by. Every week, The Big Money features a corporate-themed video that's had significant viewership on YouTube: some approved, some unapproved, some mashed-up combinations of the two. And we'll ask our readers to vote on how the video affects the brands. We think the responses will surprise you, and provide a window onto what is fast becoming the most important playground for corporate games. (Note: This feature has no official relationship to YouTube or its owner, Google.)