From the News Release:
http://comscore.com/Press_Events/Press_Releases/2009/9/Google_Sites_Surpasses_10_Billion_Video_Views_in_August

"Google Sites continued to rank as the top U.S. video property in August as it surpassed the 10 billion videos viewed threshold, representing 40 percent of all videos viewed online. YouTube.com accounted for 99 percent of all videos viewed at the Google Sites property. Microsoft Sites ranked second with 547 million (2.2 percent) followed by Viacom Digital with 539 million videos viewed (2.1 percent) and Hulu with 488 million (1.9 percent)."

"More than 161 million viewers watched an average of 157 videos per viewer during the month of August. Google Sites attracted 121.4 million unique viewers during the month (82.8 videos per viewer), followed by Microsoft Sites with 54.9 million viewers (10 videos per viewer) and Yahoo! Sites with 51.6 million viewers (6.9 videos per viewer)."