Live video on the Web is starting to take off, judging by the massive jump in traffic that Justin.tv is witnessing. According to comScore, the live video site’s global audience saw a massive jump from 9.3 million unique visitors in January to 15 million in February, which is about the same number of people who went to Veoh and nearly twice as many as visited Hulu.com. Of course, Hulu is only available in the U.S., where it is fourth most popular video site, and its videos are watched on other sites as well. In the U.S., ComScore only shows Justin.tv attracting 1.4 million people in February. So most of its audience and growth is global, with particular strength in Spain, Brazil, Germany, and the UK.

Quantcast, which directly measures all three sites, shows a similar trend. Globally, Justin.tv has 22.1 million monthly uniques, compared to 15.8 million for Hulu, and 11.9 million for Veoh. While the U.S. numbers are 3.9 million for Justin.tv, 14 million for Hulu, and 4 million for Veoh. (Ustream.tv seems to be the second-largest live video streaming site with 6.7 million global monthly visitors and 1.4 million in the U.S.). These are all site numbers, Quantcast also measures “network” numbers which presumably includes videos embedded elsewhere, and those are about double the site stats for each service. Justin.tv itself claims 1,800 percent year-over-year growth in unique visitors based on its internal Google Analytics numbers.

What all of these number show is that live video is beginning to make its mark, and could soon challenge the top video sites for the attention of audiences. There are 428,000 channels broadcasting live video on Justin.tv. Of those, 40,000 channels broadcast 1.75 million hours of video each day. And the level of engagement seems to be just as high as on regular video sites. ComScore’s VideoMetrix estimates that the average Justin.tv viewer in ethe US. watches just over an hour a month (64.7 minutes), almost exactly the same as a Veoh viewer (64.5 minutes), but still well below a Hulu viewer (87.2 minutes).

So why is Justin.tv so popular overseas? Could it be all the live sports events streamed over the service? Soccer and female wrestling seem to be particulraly popular.