The market share of U.S. visits to YouTube increased 70 percent 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 percent in the same period, writes MarketingCharts.

(Traffic data refers only to 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 percent 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 percent of visits, followed by MySpace Videos with 16 percent, and Google Video with less than 8 percent.

More video site data from Hitwise:

• Search engines are responsible for about 20 percent of traffic to 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 percent increase in the amount of traffic leaving search engines and going to video sites in the past year.