New comScore data shows 84 million U.S. Internet users watched online videos in October for an impressive average of 21.1 hours per viewer. The total U.S. Internet audience viewed 42.6 billion videos, an all time high. Google sites, driven by YouTube, ranked #1 with 161 million unique viewers and 20.9 billion videos viewed. But Facebook, which was barely a blip on the video viewing charts just a couple of years ago, came in at #2 with 59.8 million viewers.