The idea here is that you have to press play on the following videos (in vertical order) so that they all stream to you at the same time. You may need to adjust the volume on each respective network, though. Press play on the top (YouTube) video, then immediately press play on the second (Google Video), and then press play on the third (Revver). Bam, bam, bam - and you should see ‘em playing back simultaneously.
Two dueling videos would have been too few. Four dueling videos would have been too many. Make sure you scroll down far enough so that you can see all three videos on your screen at the same time, then press the play button for each video. This will only work if you play the videos on the same page together:
Because of inconsistent timing issues, each time you try this, you should see / hear slightly different results. My secondary interest lies in how many people view the video from the respective video hosting networks (though I believe that YouTube will draw the most eyeballs, Revver the most revenue, and Google the least everything).