While this is much less "WOW" than the Wario Shake experience we saw earlier but I think this is much cheaper to buy media wise. Also it's placed on existing content not specially created "viral" content.
The downside is that the syncing is not dynamic. It feels out of Sync with the video, pause the video and it's annoying.
Upside: The addition of the overlay ad is nice too.
It also reminds me of this "NSFW" banner for Nissin noodles on a "mens" site. Having the ad react to the video being viewed is fertile ground for ideas, I hope Youtube are willing to allow ads to tap into the audio waveforms of the videos in the future.