The market share of US visits to YouTube increased 70% from January 2007 to May 2007, according to Hitwise research director LeeAnn Prescott, with the share of visits to some 64 other video sites increasing only 8% in the same period. (Traffic data refers only site visits, not streams or streams from views on embedded videos.)

As of May 2007, YouTube’s market share of visits to video sites was 50% more than that of those 64 sites combined, according to Hitwise.

The top 10 list in Hitwise’s video site custom category for May is headed by YouTube, with 60% of visits, followed by MySpaces Videos with 16% and Google Video with less than 8%.

More video site data from Hitwise:

• Search engines are responsible for about 20% of traffic to all video sites.
• Hitwise captured 23,696 search terms that sent traffic to its custom category of 65 video sites in the four weeks ended June 24.
• In the corresponding year-earlier period, Hitwise captured 110,775 search terms sending traffic to the same category.
• There has been a 300% increase in the amount of traffic leaving search engines and going to video sites in the past year.