There's no shortage of YouTube killers springing up, but none of them appear to be doing their jobs, because traffic to YouTube continues to grow.

In May, YouTube accounted for more than 75 percent of U.S. traffic to video sites, according to Hitwise. MySpaceTV, which was the second most visited video site, had a 9 percent share of U.S. traffic.

YouTube's share of traffic rose 26 percent from May 2007, while its major competitors -- the supposed YouTube killers -- experienced double digit declines. MySpaceTV's share dropped 44 percent, while Google Video, the third most visited video site, experienced a 52 percent decline.

According to Information Week, 82 percent of those who logged onto YouTube in May were returning visitors.

YouTube may have a seemingly insurmountable lead when it comes to online video, but advertisers aren't fans of short-term content, and YouTube is experimenting with more long-form content, perhaps inspired by the modest success Hulu has experienced with ad sales. Google has made monetizing YouTube a top priority, but the man leading that effort, Shashi Seth, left the company earlier this month.