ComScore reports that 175 million US Internet users each watched an average of 14.4 hours of online video in September. That means for some Internet users they must get nearly all of their video content over the Internet.

Google Sites, driven primarily by video viewing at YouTube.com, ranked as the top online video content property with 144.2 million unique viewers. Yahoo! Sites captured the #2 spot with 54.4 million viewers, followed by Facebook.com with 52.2 million viewers. Microsoft Sites jumped 3 positions in September, securing fourth place with 45.5 million viewers. Google Sites had the highest number of overall viewing sessions with 1.9 billion and average time spent per viewer at 260 minutes, or 4.3 hours.

More here: http://comscore.com/Press_Events/Press_Releases/2010/10/comScore_Releases_September_2010_U.S._Online_Video_Rankings

– Hulu is the king of video ads showing nearly 28 ads per viewer.
– Number 2 and 3 Tremor Video Network and BrightRoll Video Network showed just under 7 ads per viewer.
– Google sites show just 5 ads per viewer.

Hulu is clearly trying to increase revenues as it preps for an IPO. But will too many video ads put off some viewers?

[Cross-posted at Silicon Valley Watcher]